PREHEAT oven to 350°F. Paperline 24 muffin cups.
MIX cake mix according to directions reducing oil to 1/4 cup and adding 1/2 cup peanut butter. Stir in 1 1/4 cups morsels. Fill each cup 2/3 full.
BAKE for 20 to 25 minutes or until toothpick inserted comes out clean. Transfer to wire rack. Cool completely.
COMBINE frosting, 1/2 cup morsels and remaining 1/2 cup peanut butter in medium bowl. Spread cupcakes generously with frosting, drizzle with warmed peanut butter and top with remaining morsels.
* To warm peanut butter, place peanut butter in small, plastic food storage bag; seal. Squeeze bag gently to warm peanut butter. Cut small hole from corner of bag and squeeze to drizzle.