- 1 (15.25 ounce) package yellow cake mix
- 1/3 cup butter, melted
- 1 egg
- 3 cups miniature marshmallows
- 1 (10 ounce) package peanut butter chips
- 2/3 cup light corn syrup
- 1/4 cup butter
- 2 teaspoons vanilla extract
- 2 cups crispy rice cereal (such as Rice Krispies®)
- 2 cups salted peanuts
- Preheat oven to 325 degrees F (165 degrees C). Grease a 9×13-inch baking dish.
- Stir cake mix, 1/3 cup melted butter, and egg together in bowl. Press mixture into prepared baking dish.
- Bake in the preheated oven until golden and fragrant, about 15 minutes. Spread marshmallows over crust and return to oven. Bake until marshmallows are melted, 2 to 3 minutes. Cool completely.
- Melt peanut butter chips, corn syrup, 1/4 cup butter, and vanilla extract together in a large saucepan over low heat. Stir crispy rice cereal and peanuts into corn syrup mixture. Pour peanut mixture over marshmallows. Cool completely. Chill in refrigerator until hardened, about 1 hour. Cut into 1-inch squares.