Prep your pan: Lightly grease a 9x13-inch baking pan with cooking spray or butter. For easy lifting later, line it with parchment paper, leaving a little overhang.

Melt the butter: In a large pot over low heat, melt the butter gently. Low and slow helps keep the marshmallows soft and prevents a stiff, dry bar.

Add marshmallows: Pour in the mini marshmallows and stir constantly until they’re fully melted and smooth. Avoid boiling. Once melted, stir in the vanilla extract and a small pinch of salt.

Fold in cereal: Remove the pot from the heat. Add the Rice Krispies and stir until everything is evenly coated. If using extra mini marshmallows for gooey pockets, fold them in now.

Mix in the Halloween flair: Gently fold in sprinkles, candy eyes, and seasonal candies. Reserve a few for the top so they show off nicely.

Press into the pan: Transfer the mixture to your prepared pan. Lightly grease a spatula—or your clean hands—to press the mixture down evenly. Don’t press too hard or the bars will turn dense.

Decorate: Sprinkle the reserved candies and sprinkles over the top. If using melted white chocolate or candy melts, drizzle it in zigzags for a mummy or spiderweb look. Add a few extra candy eyes for fun.

Set and slice: Let the pan sit at room temperature for 30–45 minutes to firm up. Lift out by the parchment and cut into squares or rectangles. For clean cuts, use a sharp knife greased lightly with butter.