In a bowl, whisk together the flour, the baking powder, and a pinch of salt.
In a separate bowl with a handheld mixer cream together the brown sugar, the peanut butter, and the butter.
Beat in the egg, vanilla and the coffee.
Add in the flour mixture alternately with the milk, beating well after each addition, and gently stir in 1/2 cup of the chopped chocolate.
Pour batter into a prepared 8-inch round cake pan and bake at 350 degrees for 28-34 minutes, or until a tester comes out clean.
Allow to cool slightly then invert onto a wire rack to cool completely.
If you are adding peanut butter glaze, turn the cake out directly onto a cake stand and add glaze while cake is still slightly warm.