Fudgy chocolate brownie meets peanut butter swirl for the ultimate indulgent bake. Just 6 ingredients, made in the Thermomix, with a crinkle top that looks as good as it tastes.

Nine chocolate brownies with a light brown, marbled swirled pattern on top are arranged on a light surface. The brownies are cut into even squares and spaced irregularly.

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Why You'll Love This Recipe
Recipe Ingredients
Step-by-Step Directions
Recipe Tips
Storage
📖 Recipe
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Why You'll Love This Recipe

Just 10 minutes of hands-on prep - the oven and cooling time do the rest.
No melting chocolate required - this recipe uses cocoa powder.
That marbled, crinkle top - looks bakery-worthy, no special skills required.

Recipe Ingredients

Six bowls and containers on a light surface hold plain flour, caster sugar, cubed butter, cocoa powder, peanut butter, and three eggs, each labelled with its ingredient name.

Please see the recipe card at the bottom of this post for the full ingredients and quantities.

Unsalted butter
Caster sugar
Cocoa powder - use unsweetened cocoa powder.
Eggs - use 3 large eggs.
Plain flour - also known as all-purpose flour in the US.
Peanut butter - both commercial (like Skippy or Bega) and natural peanut butter work here. Commercial peanut butter needs microwaving until runny before drizzling. Natural peanut butter often separates, with oil rising to the top - give it a good stir first, then, if it's still stiff, microwave for 30-40 seconds. A loose paste is fine to dollop and swirl through with a skewer.

Step-by-Step Directions

These step-by-step Thermomix photos are here as a visual guide. You'll find all the exact times, temperatures, and quantities in the printable recipe card below.

A square baking tin lined with greaseproof paper, filled with chocolate brownie batter, waiting to be baked, on a light marble surface.

Once you've made your brownie batter in the Thermomix, pour it into a 20cm square tin lined with baking paper, and spread evenly with the back of a spoon or spatula.

A square tin of chocolate brownies topped with swirls of peanut butter, sitting on a white marble surface. The brownies are still in the tin, lined with baking parchment.

Dollop or drizzle the melted peanut butter over the top of the brownie batter. Mine was natural peanut butter and a little thicker since it was from the end of the jar.

A square tin of brownies with a marbled swirl of chocolate and peanut butter on top, set on a light marble surface.

Use a skewer or the tip of a knife to swirl the peanut butter through the batter.

A square tin of brownies with a marbled chocolate and peanut butter pattern on top sits on a small wooden chopping board on a light marble worktop.

Bake for 30-35 minutes until the centre is just set, then leave to cool completely in the tin before slicing.

Recipe Tips

Salt: Most peanut butters already contain salt, so there's no need to add extra to this recipe. If you're using a completely unsalted peanut butter, a small pinch of salt can help balance the sweetness.

Don't skip the cooling time: Leaving the brownies to cool completely in the tin helps them set properly and makes for cleaner slices.

Storage

Store the brownies in an airtight container in a cool place for up to 3 days. They also freeze well - wrap each square individually in cling film, then store in an airtight container in the freezer for up to 3 months. Thaw at room temperature before serving.

Twelve square brownies with a marbled chocolate and peanut butter swirl pattern are arranged on a light-coloured surface.

⭐️ Did you make these Peanut Butter Swirl Brownies? I'd love to hear what you think - please leave a comment and recipe rating below! You can also subscribe to my email list to never miss a new Thermomix recipe.

📖 Recipe

Chocolate brownies with a light brown, marbled swirled pattern on top are arranged on a light surface. The brownies are cut into even squares and spaced irregularly.

Ingredients

150 g unsalted butter roughly chopped
275 g caster sugar
75 g cocoa powder unsweetened
3 large eggs
75 g plain flour
100 g peanut butter see notes

Instructions

Preheat the oven to 160°C/320°F (140°C fan). Line a 20cm square baking tin with baking paper, leaving an overhang on each side.
Add the butter, sugar and cocoa powder to the Thermomix bowl and melt for 3 min/50°C/speed 2.5.
Set the Thermomix to 1 min/speed 3 and drop the eggs in one at a time through the lid, keeping the machine running for the full minute. Scrape down the sides of the bowl with a spatula.
Tip in the flour and mix for 3 sec/speed 5. Scrape down the sides of the bowl and mix for a further 3 sec/speed 5 until well combined. Stir in any loose bits of flour with a spatula.
Pour the batter into the prepared tin. Melt the peanut butter in the microwave for approximately 30 seconds until runny, then drizzle it over the top of the chocolate batter. Use the tip of a knife or skewer to swirl it through. (See the photo in the post for guidance.)
Bake for 30-35 minutes until the centre is just set. Leave to cool completely in the tin before cutting into squares or bars.

Notes

Peanut butter: Both commercial (like Skippy or Bega) and natural peanut butter work here. Commercial peanut butter needs microwaving until runny before drizzling. Natural peanut butter often separates, with oil rising to the top - give it a good stir first, then, if it's still stiff, microwave for 30-40 seconds. A loose paste is fine to dollop and swirl through with a skewer.

Storage: Keep the brownies in an airtight container somewhere cool for up to 3 days. To freeze, wrap each square individually in cling film, then store in an airtight container in the freezer for up to 3 months. Thaw at room temperature before serving.