Step 1

Preheat the oven to 350°F (177°C) and lightly grease a 10-ounce ramekin.

Step 2

Melt 2 tablespoons of butter in a microwave-safe bowl.

Step 3

In a separate bowl, whisk together sugar, flour, and cocoa powder.

Step 4

Add the melted butter, egg yolk, and vanilla to the dry ingredients. Stir until just combined.

Step 5

Transfer the brownie batter to the greased ramekin, smoothing it into an even layer.

Step 6

In a small bowl, cream together butter and both sugars.

Step 7

Mix in the egg yolk and vanilla.

Step 8

Add flour, baking soda, and salt, stirring until just combined.

Step 9

Fold in the chocolate chips and chopped nuts.

Step 10

Layer this cookie dough over the brownie batter in the ramekin and place the filled ramekin on a rimmed baking sheet to catch any spills.

Step 11

Bake for 20-25 minutes, or until the top is golden and the brookie is cooked through. To check for doneness, insert a toothpick into the center; if it comes out clean, your brookie is ready to enjoy.