You can pretty much do this with any cereal, and we all know the original is Rice Crispies. :)
But here is my take using Trix!!!
6 cups Trix Cereal
1 bag mini marshmellows
1 tsp vanilla
1/2 cup butter
In a large pot on medium heat melt butter.
Add marshmellows and vanilla and melt, stirring constantly, until smooth.
Remove from heat and add in cereal.
Stir until completely coated.
Place mixture into a 9 x 10 greased glass cake pan.
Let cool to harden.
Cut and eat!