Lightly grease an 8x8-inch pan using nonstick spray or butter.

Melt ¼ cup of butter in a medium saucepan over low heat.

Add 4 cups of mini marshmallows to the melted butter and stir until completely melted.

Remove from heat and pour the melted mixture over 5 cups of Rice Krispies cereal, folding gently to combine.

Fold in decorative sprinkles or candy if desired.

Transfer the mixture to the greased pan and press down lightly with parchment paper.

Allow to cool at room temperature for 20–30 minutes or in the refrigerator for 5 minutes.

Decorate using melted candy melts or chocolate as desired.