Preheat oven to 325 degrees. Spray a 12-cup fluted cake pan with nonstick cooking spray with flour.

In a large bowl, beat butter, sugars, and peanut butter at medium speed with an electric mixer until fluffy. Add vanilla. Add eggs, one at a time, beating well after each addition.

In a medium bowl, combine flour, baking powder, and salt. Gradually add to butter mixture, 1 cup at a time, alternately with milk, beginning and ending with flour mixture. Beat just until combined. Stir in chocolate and peanut-butter morsels. Spoon batter into prepared pan.

Bake for 1 hour and 15 to 25 minutes, or until a wooden pick inserted in the center comes out clean. Cover top of cake with aluminum foil to prevent excess browning, if necessary.

Let cool for 10 minutes. Remove from pan, and cool completely on a wire rack. Garnish with confectioners¿ sugar and miniature peanut-butter cups, if desired.