Grease a 9×9-inch baking pan or line it with parchment paper for easy removal.

In a large saucepan, melt the butter over low heat. Add the mini marshmallows and stir until completely melted and smooth. Stir in the lemon zest and lemon extract (if using).

Remove from heat and immediately stir in the Rice Krispies cereal until well coated.

Press the mixture evenly into the prepared pan using a buttered spatula or wax paper. Don’t press too hard—you want them to stay soft and chewy.

Melt the white chocolate chips in the microwave in 20-second intervals, stirring until smooth. Drizzle over the top of the bars. Finish with a sprinkle of lemon zest or fine curls of lemon peel.

Allow the treats to cool and set for at least 30 minutes. Cut into squares and enjoy!