Directions

1. Preheat the oven to 350 degrees F (175 degrees C). Grease and flour two 8 inch round cake pans.
2. Sift together the flour, cocoa powder, baking powder and salt; set aside. Melt the bittersweet chocolate in a cup or small bowl in the microwave. Stir every 15 seconds until smooth.
3. In a large bowl, beat the butter and sugar with an electric mixer until light and fluffy. Mix in the mashed potatoes and then the eggs, one at a time. Stir in the melted chocolate. Stir in the dry ingredients alternating with the milk just until everything is mixed. Divide evenly between the prepared pans and smooth the surface if needed.
4. Bake in the preheated oven until a knife inserted into the center of the cake comes out clean, 25 to 30 minutes. Cool in the pans set over a wire rack.