In a medium saucepan, melt 3 tablespoons of unsalted butter and 4 cups of mini marshmallows over low heat, stirring continuously for about 5–7 minutes until smooth.

Remove from heat and stir in 1 cup of creamy peanut butter, mixing for 1-2 minutes until fully combined.

In a large mixing bowl, pour in 6 cups of Rice Krispies cereal and pour over the warm peanut butter-marshmallow mixture, gently folding together for about 2-3 minutes.

Prepare a muffin tin with paper liners and spoon the Rice Krispies mixture into each liner, pressing down gently to form a compact base.

Melt 1 cup of chocolate chips in the microwave in 30-second intervals, then spoon the melted chocolate over each Rice Krispie cup.

Allow to set at room temperature for about 20 minutes or refrigerate to speed up the cooling process.