01 -
Use a big bowl to mix the butter, peanut butter, white sugar, and brown sugar until it gets fluffy and smooth (around 3 minutes). Beat in the egg half and vanilla. In another bowl, stir together the flour, soda, and salt. Slowly combine the dry stuff with the wet and mix just enough to hold it all together. Set it aside for now.
02 -
Mix the melted butter and sugar in a clean large bowl. Throw in the egg and vanilla, whisking until it’s all blended well. Sift the dry ingredients—cocoa, flour, baking powder, and salt—and bit by bit, fold them into the wet mix until it’s smooth.
03 -
Turn on your oven to 350°F (175°C) and get a baking sheet ready with parchment paper. Take one tablespoon each of both doughs. Gently roll them into a ball together, twisting slightly for a marbled look. Be careful not to overdo it so they stay swirled.
04 -
Pop the dough balls onto the lined sheet, keeping them about 2 inches apart. Bake for around 10-12 minutes, or until you see the edges firm up but the centers stay soft.
05 -
Leave the cookies on the baking tray for 5 minutes to cool, then move them to a wire rack so they can cool all the way before eating.