Place butter in a pan and turn the burner to medium to low heat. Watch the butter so that it doesn't burn.
Once the butter has melted, stir in salt, vanilla extract, and mini marshmallows.
Stir the marshmallows until melted. Next, stir in Rice Krispies cereal.
Take the pan off stovetop and stir. Pour into prepared pan and spread evenly. Gently press down the Rice Krispies. Press Lucky Charms marshmallows on the top layer of treats.
Let Rice Krispies cool before lifting them out of the pan. Once out of the pan, cut the treats into squares.