Line a 9×9-inch baking pan with parchment paper, extending paper over edges of pan. Place 1 1/2 cups peanut butter in a medium microwave-safe bowl. Microwave on HIGH at 30-second intervals until melted, stirring each time. Pour melted peanut butter into prepared baking pan; spread evenly. Freeze for 20 minutes or until frozen.

Preheat oven to 350°. Lightly spray another 9×9-inch baking pan with Hy-Vee nonstick spray; set aside. Prepare brownie batter according to package directions using eggs, oil, and cold water. Spread half of brownie batter into the second prepared pan.

Use paper to lift frozen peanut butter from pan; remove parchment paper. Place peanut butter on top of brownie batter in second baking pan and top with remaining batter. Bake for 38 to 40 minutes or until a toothpick inserted near center comes out clean. Cool brownies in pan on a wire rack.

Place chocolate chips in a small microwave-safe bowl. Microwave on HIGH at 30-second intervals until melted, stirring each time. Drizzle over cooled brownies. Place remaining ½ cup peanut butter in a small microwave-safe bowl. Microwave on HIGH at 30-second intervals until melted, stirring each time; drizzle over brownies. Sprinkle with chopped peanuts. Garnish with coarse salt, if desired. Store covered at room temperature up to 5 days.