01 -
Line a 9-inch square pan with parchment paper, leaving overhang on two sides. Lightly butter the parchment if you want extra release insurance.
02 -
Melt the butter in a large saucepan over low heat. Add the mini marshmallows and stir until smooth and glossy, 3-4 minutes. Remove from the heat, fold in the cereal, and press the mixture evenly into the prepared pan. Cool for 20 minutes.
03 -
In a large bowl, beat the room-temperature cream cheese, powdered sugar, lemon juice, and vanilla until smooth and fluffy, about 2 minutes.
04 -
In a separate bowl, whip the cold heavy cream to stiff peaks. Fold it into the cream cheese mixture in two additions. Add green food coloring a few drops at a time if using.
05 -
Spread the cheesecake filling over the cooled cereal base. Cover and freeze until firm, at least 4 hours or overnight for the neatest slices.
06 -
Scatter the cereal marshmallows and sprinkles over the firm cheesecake layer. Lift the slab from the pan and cut into 16 bars with a warm knife, wiping the blade between cuts.