Heat oven to 350°F. Grease and lightly flour 12-cup fluted tube pan. Make cake according to package directions. Stir in 1/2 cup peanut butter and 1 cup chocolate chips. Pour into pan. Bake 30 to 35 minutes or until wooden pick inserted in center of cake comes out clean.
Let stand in pan 10 minutes; remove from pan to wire rack.
In small microwave-safe bowl, combine remaining chocolate chips and 1/4 cup peanut butter. Melt on HIGH (100%) 45 seconds or until chocolate is melted. Stir until combined. Drizzle over warm cake. Refrigerate 15 minutes or until icing is set.
This recipe is recommended for 12 servings.