Step 1

Add marshmallows to a large microwave-safe bowl, then remove about a cup to set aside for later.

Step 2

Add butter and heat on high for 1 minute and stir. Then heat in 30-second increments, stirring after each, until butter is melted. Add vanilla, stir until smooth and let cool slightly.

Step 3

Add reserved marshmallows, then add cereal to bowl and stir with a wooden spoon or rubber spatula until cereal is well-coated.

Step 4

Fold in mini chocolate chips until evenly distributed, mixing gently and quickly to avoid melting the chocolate chips. Transfer mixture to a buttered 9 x 9 pan and use a buttered spatula (or a layer of plastic wrap and your hands) to press down tightly. Let cool completely before cutting into bars.