Step 1

Heat oven to 350°F.

Step 2

Reserve 2 Tbsp. nuts for later use. Prepare brownie batter as directed on package; stir in remaining nuts. Spread in 13x9-inch pan sprayed with cooking spray.

Step 3

Beat cream cheese, 1/2 cup peanut butter, milk, and egg yolk in bowl with mixer until blended. Press out excess air and seal bag. Cut small piece (about 1/4 inch) from one of the bottom corners of bag. Use bag to pipe cream cheese mixture over brownie batter in pan.

Step 4

Bake 30 min. Cool completely.

Step 5

Mix frosting and remaining peanut butter in microwaveable bowl. Microwave on HIGH 30 sec.; stir. Spread over brownie. Sprinkle with reserved nuts.