Prep the pan. Line a 9x13-inch baking pan with parchment, leaving overhang for easy lifting. Lightly grease the parchment.

Melt the butter. In a large pot over low heat, melt the butter until just liquid. For extra flavor, let it brown slightly until golden and nutty, then immediately lower the heat.

Stir in marshmallows. Add the 10-ounce bag of mini marshmallows. Stir constantly over low heat until fully melted and smooth. Take your time. Don’t crank the heat or the mixture can turn tough.

Add flavor. Remove from heat. Stir in vanilla and salt. If you want pastel bars, add a drop or two of food coloring and stir until evenly tinted.

Fold in cereal. Add Rice Krispies and fold gently with a silicone spatula until coated. If using, fold in the extra 1 cup of mini marshmallows now for extra gooey pockets.

Press into pan. Transfer mixture to the prepared pan. Lightly grease your hands or a spatula and press the mixture into an even layer. Press firmly but not hard to keep the bars soft.

Decorate base layer. While still warm, scatter half the pastel M&M’s or mini eggs over the top and gently press them in so they stick without crushing them.

Make the chocolate drizzle. Melt white chocolate or candy melts in a microwave-safe bowl in 20–30 second bursts, stirring after each, until smooth. Stir in a bit of oil to thin if needed. Divide into bowls and tint with pastel food coloring if you like.

Drizzle and sprinkle. Drizzle the melted chocolate over the treats in zigzags. Finish with sprinkles and the remaining candies for a pretty, speckled look.

Set and slice. Let the pan sit at room temperature for 45–60 minutes, or until set. Lift out using the parchment and slice into 18–24 bars using a sharp, greased knife.