Grease a 9x9-inch baking pan or line it with parchment paper.

Melt ¼ cup of butter in a saucepan over low heat, then add in both mini marshmallows and stir until smooth and glossy.

Remove from heat and stir in lemon zest and lemon extract.

Fold in 6 cups of Rice Krispies cereal until thoroughly combined.

Transfer the mixture to the prepared pan and press down evenly with a spatula.

Melt 1 cup of white chocolate chips in a microwave-safe bowl, stirring until smooth.

Drizzle the melted white chocolate over the crisp treats and optionally sprinkle with more lemon zest.

Allow to cool at room temperature for 30 minutes before cutting into squares.