*Percent Daily Values are based on a 2,000 calorie diet. Your daily values may be higher or lower depending on your calorie needs.
**Nutrient information is not available for all ingredients. Amount is based on available nutrient data.
(-)Information is not currently available for this nutrient. If you are following a medically restrictive diet, please consult your doctor or registered dietitian before preparing this recipe for personal consumption.
Preheat oven to 350 degrees F (175 degrees C). Grease a 9x13-inch baking dish.
Beat brownie mix, vegetable oil, water, and 2 eggs in a bowl until batter is smooth.
Whisk flour, baking powder, and salt together in a small bowl.
Beat peanut butter, brown sugar, and 2 tablespoons butter together in another bowl with an electric mixer until light and creamy. Beat 1 egg and vanilla into peanut butter mixture until fluffy. Stir flour mixture into peanut butter mixture until just blended.
Pour brownie batter in the prepared baking dish. Drop peanut butter mixture by small spoonfuls over the brownie batter.
Bake brownies in the preheated oven until a toothpick inserted in the center of the brownies comes out clean, about 30 minutes; cool.
Melt 1/4 cup butter in a large saucepan over medium heat; add marshmallows and stir until marshmallows are melted. Cook mixture until butter and marshmallow flavors are combined, about 2 minutes; remove from heat.
Spread 1/3 the marshmallow mixture over the cooled brownies. Stir crispy rice cereal into remaining 2/3 the marshmallow mixture; press in an even layer on top of the brownies. Refrigerate until set, about 15 minutes; cut into squares.