Preheat the oven to 350 degrees. Grease and lightly flour 12 individual (about 1 cup size) bundt tins.
In the bowl of an electric mixer, fitted with a paddle, cream the butter and sugar together. In a small mixing bowl, sift together the flour, baking powder, baking soda and salt and set aside. Add the eggs, one at a time, to the butter mixture. Mix well after each egg. Add the chocolate and vanilla. Mix well. Add the sifted flour mixture, 1/2 cup at a time, alternating with the milk. Mix well. Fill each tin 1/2 full with the batter. Place some of the peanut butter chips in the center of the batter. Pour the remaining batter over the chips. Place in the oven and cook for about 18 to 20 minutes. Remove from the oven and cool for a couple of minutes in the pan. Invert the cakes onto a wire rack. In a small mixing bowl, combine the cocoa powder, powdered sugar and milk. Mix until smooth. Spoon some of the glaze over each bundt cake. Allow the glaze to set, then serve.