Preheat oven to 425 degrees. Spray 2 8 oz. ramekins with non-stick cooking spray. Place 1 tablespoon of cocoa powder in the first ramekin. Swirl the cocoa powder all around the ramekin and tap out the extra in the second ramekin. Add in the remaining ½ tablespoon of cocoa powder and discard the excess cocoa powder once ramekin is covered.
In a medium-sized microwave-safe bowl, add in the chopped semi-sweet chocolate and butter. Microwave in 30 second intervals and stir after each 30 seconds. Do this 3 to 4 times until the chocolate is smooth and completely melted.
Set aside and let cool for 10 minutes.
Add in the granulated sugar and eggs and whisk until thoroughly incorporated.
Add in the all-purpose flour. Using a spatula, mix until the flour is barely combined.
Pour batter into the 2 ramekins.
Place a large teaspoon of the peanut butter in the center of each ramekin. Make sure to press it down a little and cover it with the cake batter.
Place the two ramekins on a quarter sheet pan and place in the oven. Bake for about 14 minutes. The outside of the cakes will be baked and the center will still be very jiggly.
Serve immediately. If you're feeling crazy, add a scoop of ice cream to the cake.