Preheat oven to 350. Grease and flour a 12 cup Bunt pan and set aside.
In large bowl combine all ingredients except chocolate chips and 1/3 cup peanut butter and beat on low speed until combined; then beat three minutes at medium speed.
By hand, stir in 1/2 cup chocolate chips.
Spoon batter into pan. Bake for 55-65 minutes until set brown, and toothpick inserted in center comes out clean (except some chocolate might stick to the toothpick).
Cool in pan for 10 minutes, then loosen edges and tum pan onto serving plate. Cool completely, then frost.
In small saucepan, melt 1-1/2 cups chocolate chips with 1/3 cup peanut butter. You can also melt these two ingredients in a small bowl in the microwave oven for 2 minutes at 50% power, stirring until smooth. Spoon over cake.