Spicy Caramelized Onion and Pepper Jack Casserole

Quick Recipe Version (TL;DR)

• Yield: 6 servings
• Prep Time: 20 minutes
• Cook Time: 55 minutes
• Total Time: 1 hour 15 minutes

Quick Ingredients

• 3 large sweet or yellow onions (about 2 1/2 lb), thinly sliced
• 3 tbsp unsalted butter + 2 tbsp olive oil (for onions)
• 2 poblano peppers + 2 jalapeños, roasted and chopped (or 1 (4 oz) can diced green chiles)
• 3 cups (12 oz / 340 g) shredded pepper jack cheese, divided
• 4 oz (115 g) cream cheese, softened
• 1 cup (240 ml) half-and-half or heavy cream
• 2 large eggs
• 1 1/2 tsp kosher salt, 1/2 tsp black pepper
• 1/2 tsp smoked paprika, 1/2 tsp ground cumin, pinch red pepper flakes (optional)
• 1/2 cup (25 g) panko breadcrumbs + 1 tbsp melted butter (for topping)
• Chopped cilantro or green onions, for serving (optional)

Do This

• 1. Slowly caramelize sliced onions in butter and olive oil with a pinch of salt, 25–30 minutes, until deep golden and jammy.
• 2. Roast poblanos and jalapeños under the broiler until blistered, steam in a covered bowl, then peel, seed, and slice or chop.
• 3. Heat oven to 375°F (190°C). Grease a 2-quart baking dish or 9×9-inch pan.
• 4. Whisk eggs, cream, cream cheese, salt, pepper, smoked paprika, cumin, and red pepper flakes. Stir in 2 cups pepper jack.
• 5. Fold caramelized onions and roasted chilies into the creamy cheese mixture, then spread evenly in the baking dish.
• 6. Top with remaining 1 cup pepper jack. Toss panko with melted butter and sprinkle over the top.
• 7. Bake 20–25 minutes until bubbly and browned. Rest 10 minutes, garnish with herbs, and serve warm.

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Why You’ll Love This Recipe

• Deep, slow-cooked caramelized onions bring natural sweetness that balances the spicy, roasted chilies.
• Creamy pepper jack and a silky custard base bake into a rich, scoopable casserole with a gorgeous bubbly top.
• Perfect as a cozy side, a vegetarian main, or a hearty dip with crusty bread or tortilla chips.
• Make-ahead friendly and flexible: easily tone down or amp up the heat to match your crowd.

Grocery List

• Produce: Sweet or yellow onions, poblano peppers, jalapeños (or canned green chiles), fresh cilantro or green onions (optional).
• Dairy: Unsalted butter, pepper jack cheese, cream cheese, half-and-half or heavy cream, eggs.
• Pantry: Olive oil, panko breadcrumbs, kosher salt, black pepper, smoked paprika, ground cumin, red pepper flakes (optional, for extra heat).

Full Ingredients

For the Caramelized Onions

• 3 large sweet or yellow onions (about 2 1/2 lb / 1.1 kg), peeled, halved, and thinly sliced
• 3 tbsp unsalted butter
• 2 tbsp olive oil
• 1/2 tsp kosher salt (to help draw out moisture)

For the Roasted Chilies

• 2 poblano peppers
• 2 jalapeño peppers (seeded for mild, seeds left in for hotter), or substitute 1 (4 oz / 113 g) can diced green chiles for milder heat
• Pinch of kosher salt (to season after roasting)

For the Creamy Pepper Jack Base

• 4 oz (115 g) cream cheese, softened
• 1 cup (240 ml) half-and-half or heavy cream
• 2 large eggs
• 3 cups (12 oz / 340 g) shredded pepper jack cheese, divided
• 1 tsp kosher salt
• 1/2 tsp freshly ground black pepper
• 1/2 tsp smoked paprika
• 1/2 tsp ground cumin
• 1/4 tsp red pepper flakes (optional, for extra heat)

For Assembly & Topping

• 1/2 cup (25 g) panko breadcrumbs
• 1 tbsp unsalted butter, melted
• Neutral oil or butter for greasing the baking dish
• Chopped fresh cilantro or thinly sliced green onions, for garnish (optional)

Step-by-Step Instructions

Step 1: Slowly Caramelize the Onions

In a large, wide skillet, heat the butter and olive oil over medium heat until the butter is melted and foamy. Add the sliced onions and 1/2 teaspoon kosher salt. Toss well to coat every strand in the fat. Cook for 5–7 minutes, stirring occasionally, until the onions begin to soften and turn translucent.

Reduce the heat to medium-low. Continue to cook, stirring every few minutes, scraping up any browned bits from the bottom of the pan. If the onions start to stick or brown too quickly, add a tablespoon of water to deglaze and lower the heat slightly. Keep cooking until the onions are deeply golden, very soft, and jammy, about 25–30 minutes total. Turn off the heat and set aside to cool slightly while you prepare the chilies and custard.

Step 2: Roast and Prepare the Chilies

While the onions caramelize, roast your peppers. Position an oven rack about 6 inches (15 cm) from the broiler and heat the broiler on high. Place the poblanos and jalapeños on a foil-lined baking sheet. Broil, turning every 2–3 minutes, until the skins are blistered and blackened in spots on all sides, 8–10 minutes total.

Transfer the hot peppers to a bowl and cover tightly with a plate or plastic wrap. Let them steam for 10 minutes; this loosens the skins. Once cool enough to handle, peel off the blistered skins with your fingers, remove stems and seeds, and slice or chop the flesh into thin strips or small pieces. Sprinkle with a pinch of salt. Set aside. (If using canned green chiles, simply drain well and pat dry with paper towels.)

Step 3: Preheat the Oven and Prepare the Dish

Preheat your oven to 375°F (190°C). Grease a 2-quart (about 2 L) baking dish or a 9×9-inch (23×23 cm) pan with butter or a light coating of oil. This helps prevent sticking and makes cleanup easier. If you prefer a rustic look and extra heat retention, you can also use a well-seasoned 10-inch cast iron skillet instead of a baking dish.

Step 4: Make the Creamy Pepper Jack Custard

In a large mixing bowl, add the softened cream cheese. Beat with a whisk or fork until smooth. Pour in the half-and-half (or heavy cream) and whisk until mostly combined; a few small cream cheese specks are fine. Add the eggs, 1 teaspoon kosher salt, black pepper, smoked paprika, ground cumin, and red pepper flakes (if using). Whisk until the mixture is smooth and evenly mixed.

Stir in 2 cups (about 8 oz / 225 g) of the shredded pepper jack cheese, reserving the remaining 1 cup (about 4 oz / 115 g) for the top. The mixture will be fairly loose; it will set as it bakes.

Step 5: Fold In the Onions and Chilies

Add the caramelized onions and roasted chilies to the bowl with the creamy pepper jack mixture. Use a spatula to gently fold everything together until the onions and peppers are evenly distributed. Taste a small spoonful (if desired) and adjust seasoning with a pinch more salt or pepper, keeping in mind that the flavors will intensify as it bakes.

Pour the mixture into the prepared baking dish or skillet and spread it into an even layer, making sure the onions and chilies are not clumped in just one area.

Step 6: Add the Topping and Bake Until Bubbly

In a small bowl, combine the panko breadcrumbs with the melted butter, stirring until all the crumbs are lightly coated. Sprinkle the reserved 1 cup shredded pepper jack evenly over the surface of the casserole. Then scatter the buttery panko crumbs over the cheese in an even layer.

Transfer the dish to the preheated 375°F (190°C) oven. Bake for 20–25 minutes, until the casserole is bubbling around the edges, the cheese is fully melted, and the top is golden brown in spots. If you like a deeper, more blistered top, you can switch the oven to broil for the last 1–2 minutes; watch closely to prevent burning.

Step 7: Rest, Garnish, and Serve

Remove the casserole from the oven and let it rest on a cooling rack for about 10 minutes. This brief rest helps the creamy custard firm up slightly, so it scoops cleanly while still staying luxuriously soft and melty.

Just before serving, sprinkle with chopped cilantro or sliced green onions for a fresh, bright contrast to the rich, spicy casserole. Serve hot or warm on its own, alongside grilled meats, or with crusty bread, tortillas, or tortilla chips for scooping.

Pro Tips

• Go low and slow on the onions. Rushing caramelization leads to browned but still sharp-tasting onions. Keep the heat on medium-low and take the full 25–30 minutes for deep sweetness.
• Deglaze for extra flavor. If the pan gets too dry, splash in 1–2 tablespoons of water, broth, or dry white wine and scrape up the browned bits for even more savory depth.
• Shred your own cheese. Pre-shredded cheese often has anti-caking agents that inhibit melting. Freshly shredded pepper jack melts more smoothly and gives a creamier texture.
• Control the heat level. For a mild casserole, seed the jalapeños thoroughly or swap them for canned mild green chiles. For extra kick, leave some seeds in or add a pinch more red pepper flakes.
• Let it rest before cutting in. A short 10-minute rest makes the layers hold together better, so you get those beautiful scoops with visible ribbons of onion and chilies.

Variations

• Bacon and onion version: Cook 4–6 slices of chopped bacon until crisp, remove and drain, then caramelize the onions in the bacon fat plus 1 tablespoon butter. Stir the bacon into the casserole before baking.
• Mushroom and onion casserole: Sauté 8 oz (225 g) sliced cremini mushrooms in a bit of butter until browned and their moisture evaporates. Fold into the onion and chili mixture for an earthier, more substantial dish.
• Mac-style bake: Stir 2 cups (about 8 oz / 225 g) cooked short pasta (such as elbow macaroni or small shells) into the creamy onion mixture before baking for a spicy, caramelized-onion mac-and-cheese-style casserole.

Storage & Make-Ahead

To store leftovers, let the casserole cool completely, then cover the dish tightly or transfer portions to airtight containers. Refrigerate for up to 3–4 days. Reheat individual portions in the microwave until hot, or rewarm larger amounts in a 350°F (175°C) oven for 15–20 minutes, loosely covered with foil, until heated through and bubbly.

For make-ahead, you can assemble the unbaked casserole (through adding the cheese and panko topping), cover tightly, and refrigerate for up to 24 hours. When ready to cook, let it sit at room temperature for 20–30 minutes while the oven preheats, then bake as directed, adding a few extra minutes if needed. This dish can also be frozen unbaked for up to 2 months; thaw overnight in the refrigerator before baking.

Nutrition (per serving)

Approximate values per serving (1/6 of the recipe): about 500 calories, 20 g protein, 22 g carbohydrates, 40 g fat, 1–2 g fiber, and 800–900 mg sodium (will vary based on exact cheeses, salt, and chilies used).