Peanut Butter Chocolate Marble Banana Loaf with Roasted Peanuts

Quick Recipe Version (TL;DR)

• Yield: 10 slices (10 servings)
• Prep Time: 20 minutes
• Cook Time: 55–65 minutes
• Total Time: 1 hour 20 minutes

Quick Ingredients

• 3 large very ripe bananas, mashed (about 1 1/2 cups / 340 g)
• 1/2 cup (113 g) unsalted butter, melted and cooled slightly
• 1/2 cup (130 g) creamy no-stir peanut butter
• 3/4 cup (150 g) granulated sugar
• 1/4 cup (50 g) light brown sugar, packed
• 2 large eggs, room temperature
• 2 tsp vanilla extract
• 1 3/4 cups (220 g) all-purpose flour
• 1 tsp baking soda + 1 tsp baking powder
• 1/2 tsp fine salt
• 1/2 tsp ground cinnamon (optional)
• 1/4 cup (20 g) unsweetened cocoa powder
• 2 tbsp (25 g) granulated sugar (for chocolate swirl)
• 2–3 tbsp milk (for chocolate swirl)
• 1/2 cup (70 g) roasted salted peanuts, roughly chopped (plus 2 tbsp extra for topping)

Do This

• 1. Heat oven to 350°F (175°C). Grease and line a 9 x 5 in (23 x 13 cm) loaf pan with parchment.
• 2. Mash bananas; whisk in melted butter, peanut butter, sugars, eggs, and vanilla until smooth.
• 3. Fold in flour, baking soda, baking powder, salt, and cinnamon just until no dry streaks remain. Stir in most of the chopped peanuts.
• 4. Transfer about 1 1/2 cups of batter to a bowl; whisk in cocoa, the extra 2 tbsp sugar, and 2–3 tbsp milk to make a chocolate batter.
• 5. Alternate spoonfuls of plain and chocolate batters in the pan. Swirl gently with a knife; sprinkle with remaining peanuts.
• 6. Bake 55–65 minutes, until a tester comes out clean. Cool in pan 15 minutes, then on a rack. Slice when barely warm.

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Why You’ll Love This Recipe

• It marries three favorites in one loaf: banana bread, chocolate swirl cake, and peanut butter.
• Bold cocoa ribbons and roasted peanut bits give every slice beautiful marbling and serious texture.
• Simple pantry ingredients; no mixer required and everything comes together in one bowl plus a small extra for the swirl.
• Stays moist for days and freezes well, making it perfect for breakfasts, snacks, or gifting.

Grocery List

• Produce: Very ripe bananas (3 large)
• Dairy: Unsalted butter, milk, eggs
• Pantry: All-purpose flour, granulated sugar, light brown sugar, creamy peanut butter, unsweetened cocoa powder, roasted salted peanuts, vanilla extract, baking soda, baking powder, salt, ground cinnamon (optional)

Full Ingredients

For the Peanut-Butter Banana Batter

• 3 large very ripe bananas, peeled and mashed (about 1 1/2 cups / 340 g)
• 1/2 cup (113 g) unsalted butter, melted and slightly cooled
• 1/2 cup (130 g) creamy no-stir peanut butter
• 3/4 cup (150 g) granulated sugar
• 1/4 cup (50 g) light brown sugar, packed
• 2 large eggs, at room temperature
• 2 tsp pure vanilla extract
• 1 3/4 cups (220 g) all-purpose flour, spooned and leveled
• 1 tsp baking soda
• 1 tsp baking powder
• 1/2 tsp fine sea salt or table salt
• 1/2 tsp ground cinnamon (optional, but delicious)

For the Bold Cocoa Swirl

• About 1 1/2 cups of the prepared peanut-butter banana batter (taken from above)
• 1/4 cup (20 g) unsweetened cocoa powder
• 2 tbsp (25 g) granulated sugar
• 2–3 tbsp milk (any kind: dairy or unsweetened non-dairy), enough to loosen into a thick pourable batter

For the Roasted Peanut Bits & Topping

• 1/2 cup (70 g) roasted salted peanuts, roughly chopped
• 2 tbsp (about 15–20 g) extra chopped roasted peanuts, for sprinkling on top

Equipment

• 9 x 5 inch (23 x 13 cm) loaf pan
• Parchment paper
• 2 medium mixing bowls (one for main batter, one for chocolate swirl)
• Whisk and rubber spatula
• Butter knife or skewer for swirling
• Wire cooling rack

Step-by-Step Instructions

Step 1: Prep the pan, oven, and peanuts

Preheat your oven to 350°F (175°C). Grease a 9 x 5 inch (23 x 13 cm) loaf pan with butter or non-stick spray. Line the bottom and long sides with a strip of parchment paper, leaving overhang as a sling so you can lift the loaf out easily later. Lightly grease the parchment as well.

Roughly chop the roasted salted peanuts. Set aside 2 tablespoons for the topping and keep the rest for folding into the batter. If your peanuts are unsalted or not very toasted, you can briefly toast them in a dry skillet over medium heat for 3–5 minutes until fragrant and lightly deepened in color, then cool completely before using.

Step 2: Mash the bananas and mix the wet ingredients

In a medium mixing bowl, mash the 3 very ripe bananas with a fork until mostly smooth; a few small lumps are fine and add texture. Whisk in the melted butter and creamy peanut butter until you have a thick, cohesive mixture with no streaks of fat or peanut butter left.

Add the granulated sugar, light brown sugar, eggs, and vanilla. Whisk well for about 1 minute, until the mixture looks slightly lighter and glossy. This helps dissolve the sugar and gives a more tender crumb later.

Step 3: Add the dry ingredients and roasted peanuts

In the same bowl (for a true one-bowl batter), sprinkle the flour, baking soda, baking powder, salt, and optional cinnamon evenly over the wet mixture. Use a rubber spatula to gently fold everything together, scraping down the sides and bottom of the bowl. Stop as soon as you no longer see dry streaks of flour; some small lumps are fine. Overmixing can make the loaf tough.

Fold in most of the chopped roasted peanuts, reserving the 2 tablespoons you set aside earlier for the top. The batter will be thick but scoopable and smell strongly of banana and peanut butter.

Step 4: Make the bold chocolate batter

Transfer about 1 1/2 cups of the peanut-butter banana batter into a separate bowl. To this smaller portion, add the unsweetened cocoa powder and 2 tbsp granulated sugar. Begin mixing, then add 2–3 tbsp milk, a little at a time, stirring until the chocolate batter is smooth, shiny, and just slightly looser than the plain batter. It should be thick but scoopable, not runny. This will create striking dark cocoa ribbons that bake up fudgy and rich against the lighter peanut-banana crumb.

Step 5: Layer and marble the batters

To build the marble effect, spoon large dollops of the plain peanut-butter banana batter into the prepared loaf pan, leaving some gaps between them. Fill those gaps with dollops of the chocolate batter. Repeat with a second layer, alternating plain and chocolate batters until both are used up. Try to distribute evenly so every slice has both flavors.

Using a butter knife or thin spatula, insert it into the batter so it just touches the bottom of the pan. Drag it through the batter in gentle S-shapes or figure-eights from one short end of the pan to the other. Make 3–4 passes only; too much swirling will blend the batters instead of marbling them.

Sprinkle the reserved chopped roasted peanuts evenly over the top for a crunchy, toasty finish.

Step 6: Bake the loaf

Place the pan on the middle rack of the preheated oven and bake for 55–65 minutes. Begin checking at 55 minutes. The loaf is done when the top is deeply golden, the peanuts are nicely toasted, and a toothpick or thin skewer inserted into the center (avoid a chocolate pocket for a true test) comes out with a few moist crumbs but no wet batter.

If the top is browning too quickly before the center is done, loosely tent the pan with foil for the last 10–15 minutes of baking. Every oven is a bit different, so use visual and toothpick cues as your guide.

Step 7: Cool, slice, and serve

Remove the pan from the oven and set it on a wire rack. Let the loaf cool in the pan for 15–20 minutes to set the structure. Then, use the parchment sling to gently lift the loaf out of the pan and place it directly on the rack to cool further. For the cleanest slices and best marble definition, let it cool until just barely warm or at room temperature, about 1 hour more.

Slice with a sharp serrated knife into 10 thick slices. Each slice should reveal dramatic dark cocoa swirls, pale golden peanut-butter banana crumb, and crunchy roasted peanut bits scattered throughout. Enjoy slightly warm, at room temperature, or lightly toasted with an extra swipe of peanut butter on top.

Pro Tips

• Use very ripe bananas: The more speckled and dark the skins, the sweeter and more flavorful your loaf will be. Underripe bananas will make it drier and less aromatic.
• Measure flour accurately: For best texture, spoon flour into your measuring cup and level it off, or weigh it (220 g). Too much flour = dense, dry bread.
• Do not over-swirling: Limit yourself to a few gentle passes with the knife. Overmixing will muddy the colors and blur the marble effect.
• Check doneness in a pale area: Insert your tester into a lighter section of the loaf. Chocolate zones can look wetter even when fully baked.
• Room-temperature ingredients help: Let eggs come to room temp so they blend smoothly and help the loaf rise evenly.

Variations

• Extra chocolatey swirl: Stir 1/4 cup (45 g) mini chocolate chips into the chocolate batter for melted pockets of chocolate throughout the dark ribbons.
• Nutty mix-up: Swap half the peanuts for chopped roasted almonds, pecans, or hazelnuts for a different flavor profile while keeping the same crunch.
• Banana loaf muffins: Divide the marbled batters among a lined 12-cup muffin pan (about 3/4 full) and bake at 350°F (175°C) for 18–22 minutes, or until a tester comes out clean.

Storage & Make-Ahead

Let the loaf cool completely before storing. Wrap tightly in plastic wrap or foil, or place in an airtight container. It will keep at room temperature for 3 days. For longer storage, refrigerate for up to 5 days; bring to room temperature or gently warm slices before serving for the best texture and flavor.

To freeze, wrap the whole loaf or individual slices tightly in plastic wrap, then in foil or a freezer bag. Freeze for up to 3 months. Thaw overnight in the refrigerator or at room temperature for a few hours. Toasting or briefly warming slices in the oven or microwave brings the peanut butter and chocolate aromas back to life beautifully.

Nutrition (per serving)

Approximate values per slice (1 of 10): about 410 calories, 23 g fat, 50 g carbohydrates, 9 g protein, 3 g fiber, 26 g sugars, 330 mg sodium. These numbers are estimates and will vary based on exact ingredients and brands used.