Melt the butter and vanilla over low heat in a heavy bottom pot.
Once the butter has melted add the marshmallows on low/medium heat and mix until gooey and melted.
Add the sugar free cereal and mix through until all the coated with the melted marshmallow mixture.
Transfer to an 8" x 8" baking pan lined with parchment paper.
Spread the cereal mixture evenly into the pan and place another parchment paper on top to press down and level the crispy treats.Remove top layer of parchment paper and allow to cool.
Once cooled remove from the pan by lifting the parchment paper, place on a cutting board and cut into squares.
Refer to the detailed video instructions below if further clarification is needed.
Video
Notes
Tip: Don't overcook the marshmallow, once they are melted add the cereal and mix through and remove from the heat.