Mustard Herb Foil Packet Brats with Potatoes and Onions

Quick Recipe Version (TL;DR)

• Yield: 4 servings (4 foil packets)
• Prep Time: 15 minutes
• Cook Time: 35 minutes
• Total Time: 50 minutes

Quick Ingredients

• 4 bratwursts (about 12–16 oz / 340–450 g total)
• 1 1/2 lb (680 g) Yukon Gold potatoes, thinly sliced (1/4 in)
• 1 large yellow onion, thinly sliced
• 2 tbsp (30 g) Dijon mustard
• 1 tbsp (15 g) whole-grain mustard
• 2 tbsp (30 ml) olive oil
• 2 tbsp (28 g) unsalted butter, cut into 4 pieces
• 1 tbsp chopped fresh parsley
• 1 1/2 tsp chopped fresh thyme (or 1/2 tsp dried)
• 1 tsp chopped fresh rosemary (or 1/4 tsp dried), optional
• 1 tsp kosher salt, plus more to taste
• 1/2 tsp black pepper
• 1/2 tsp garlic powder
• 1/4 cup (60 ml) chicken broth (or beer)

Do This

• 1. Heat oven to 425°F (220°C). Tear 8 sheets heavy-duty foil (about 12×18 in) for 4 double-layer packets.
• 2. Toss potatoes + onions with mustards, oil, salt, pepper, garlic powder, and herbs.
• 3. Divide potato mix among foil sheets; add 1 brat per packet.
• 4. Add 1 tbsp broth and 1/2 tbsp butter to each packet; seal tightly.
• 5. Bake on a sheet pan for 30 minutes; carefully open packets and bake 5 minutes more to brown.
• 6. Rest 5 minutes, sprinkle with parsley, and serve straight from the foil or plated.

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Why You’ll Love This Recipe

• All-in-one dinner: Brats, potatoes, and onions cook together in one tidy foil packet.
• Big flavor, minimal effort: Mustard and herbs create a savory, tangy coating that tastes slow-cooked.
• Easy cleanup: No pan scrubbing if you serve right from the foil.
• Flexible cooking method: Works great in the oven and adapts easily for the grill.

Grocery List

• Produce: 1 1/2 lb (680 g) Yukon Gold potatoes, 1 large yellow onion, fresh parsley, fresh thyme (and optional fresh rosemary)
• Dairy: unsalted butter
• Pantry: Dijon mustard, whole-grain mustard, olive oil, kosher salt, black pepper, garlic powder, chicken broth (or beer), heavy-duty aluminum foil

Full Ingredients

Main

• Bratwurst: 4 bratwursts (about 12–16 oz / 340–450 g total)
• Potatoes: 1 1/2 lb (680 g) Yukon Gold potatoes, scrubbed and thinly sliced to 1/4-inch (6 mm)
• Onion: 1 large yellow onion, thinly sliced

Mustard-Herb Seasoning

• 2 tbsp (30 g) Dijon mustard
• 1 tbsp (15 g) whole-grain mustard
• 2 tbsp (30 ml) olive oil
• 1 tsp kosher salt
• 1/2 tsp black pepper
• 1/2 tsp garlic powder
• 1 1/2 tsp fresh thyme, chopped (or 1/2 tsp dried thyme)
• 1 tsp fresh rosemary, chopped (or 1/4 tsp dried rosemary), optional
• 1 tbsp fresh parsley, chopped (plus more for serving)

For Steam and Finish

• 1/4 cup (60 ml) chicken broth (or beer), divided
• 2 tbsp (28 g) unsalted butter, cut into 4 equal pieces

Equipment

• Heavy-duty aluminum foil (or regular foil, doubled)
• Rimmed baking sheet

Step-by-Step Instructions

Step 1: Heat the oven and prep the foil

Preheat your oven to 425°F (220°C). Set a rimmed baking sheet on the counter (you’ll build the packets on it to keep things neat).

Tear 8 sheets of heavy-duty foil, each about 12×18 inches, and stack them into 4 double-layer sets. Double layers help prevent leaks and torn packets.

Step 2: Slice the potatoes and onions for even cooking

Thin slices are the key to tender potatoes in a reasonable time. Slice the potatoes to about 1/4-inch (6 mm) thick. Thinly slice the onion as well so it softens and sweetens in the packet.

Place the potatoes and onions in a large mixing bowl.

Step 3: Mix the mustard-herb coating

Add the Dijon mustard, whole-grain mustard, olive oil, kosher salt, black pepper, garlic powder, thyme, optional rosemary, and parsley to the bowl.

Toss thoroughly until the potatoes and onions look evenly coated. Take a moment here to separate any potato slices that are sticking together so they cook evenly.

Step 4: Assemble the foil packets

Divide the potato-onion mixture evenly among the 4 foil sets, placing it in a mound in the center of each. Top each mound with 1 bratwurst.

Drizzle 1 tbsp (15 ml) broth (or beer) into each packet and add 1 piece of butter (that’s 1/2 tbsp per packet). The liquid creates steam for tender potatoes, while the butter rounds out the mustard’s tang.

Step 5: Seal tightly to trap steam

Bring the long sides of foil up and over the food, fold together tightly, then fold in the ends to seal. You want a snug packet with a little air space inside, but no gaps where steam can escape.

Place the packets seam-side up on the baking sheet.

Step 6: Bake until the potatoes are tender and the brats are cooked through

Bake for 30 minutes at 425°F (220°C).

Carefully open one packet (watch for hot steam) and pierce a potato slice with a fork. It should be tender. If the potatoes are still firm, reseal and bake for 5 more minutes, then check again.

Once tender, open all packets (leave the foil edges turned up to prevent drips) and return them to the oven for 5 minutes to dry out excess moisture and lightly brown the brats and potatoes.

Doneness note: Bratwurst should reach an internal temperature of 160°F (71°C) when checked with a thermometer.

Step 7: Rest, garnish, and serve

Let the packets rest for 5 minutes so the juices settle and the steam finishes the potatoes.

Sprinkle with a bit more chopped parsley. Serve straight from the foil for a rustic feel, or plate the brat with a generous scoop of mustardy potatoes and onions.

Pro Tips

• Slice matters: Keep potatoes at 1/4-inch so they cook through in the stated time. Thicker slices may need an extra 10–15 minutes.
• Prevent sticking: Make sure potatoes are well-coated with the oil-and-mustard mixture before sealing the packets.
• For extra browning: After opening the packets, switch to broil (high) for 2–3 minutes, watching closely to avoid scorching.
• Thermometer wins: Because brat sizes vary, checking for 160°F (71°C) guarantees they’re safely cooked.
• Keep the steam in: If a packet leaks, wrap it in a second layer of foil to avoid drying out the potatoes.

Variations

• Beer-and-onion version: Use lager instead of broth and add an extra 1/2 cup sliced onions (great with whole-grain mustard).
• Spicy mustard kick: Swap the Dijon for spicy brown mustard and add 1/4 tsp crushed red pepper flakes.
• Add a veggie: Add 1 sliced bell pepper (about 150 g) to the bowl with the onions and potatoes for extra sweetness and color.

Storage & Make-Ahead

Refrigerate: Cool leftovers within 2 hours, then store in an airtight container for up to 3 days. (It’s best to remove food from the foil for storage.)

Reheat: Warm in a 375°F (190°C) oven for 12–15 minutes until hot, or microwave in 60–90 second bursts. For better texture, reheat on a sheet pan and broil for 1–2 minutes at the end.

Make-ahead: Slice potatoes and onions up to 24 hours ahead. Keep potatoes submerged in cold water in the fridge to prevent browning, then drain and pat very dry before tossing with mustard and oil. You can also assemble packets up to 8 hours ahead and refrigerate; add 5 minutes to the bake time if starting from cold.

Nutrition (per serving)

Approximate, based on 1 bratwurst and one-quarter of the potato mixture: 650 calories, 34 g protein, 39 g fat, 44 g carbohydrates, 4 g fiber, 6 g sugar, 1200 mg sodium.