Preheat your oven to 350°F (175°C). Cream together the softened butter and sugar until light and fluffy, about 3 to 5 minutes.

Add the room temperature eggs and vanilla extract to the mixture, and mix until just combined.

In a separate bowl, whisk together the flour and cocoa powder. Gradually add to the wet mixture, blending carefully.

Divide the dough, leaving one half plain and mixing the other half with an additional 1/3 cup of cocoa powder.

On a lined baking sheet, drop alternating dollops of the vanilla and chocolate dough.

Using a toothpick, gently swirl the dollops together to create a zebra pattern.

Bake the cookies for 10 to 12 minutes until the edges are slightly golden and the center remains soft.

Let the cookies cool on the baking sheet for 5 minutes before transferring to a wire rack.