Grease an 8x12 inch baking pan with cooking spray and set aside. (See notes.)

Melt butter in a large saucepan over low heat.

Add marshmallows and stir until coated in butter. Melt over low heat, stirring occasionally.

Once marshmallows are completely melted, add green food coloring. Start with 7-8 drops and add more until it’s the right color. Stir well.

Turn off heat and carefully stir in Rice Krispies cereal until it’s completely coated.

Spread the green Rice Krispie mixture into the prepared pan and use a spatula (or your hands) to pat into an even layer. It will be sticky so it helps to spray your hands or spatula with cooking spray.

Cover the top of the trees with a layer of sprinkles. (You need to do this immediately so they will stick.) Let the Rice Krispies cool for at least 10 minutes to allow them to firm up.

Cut into tree shapes. Start with a line cutting your pan in half down the longest side to give you two long rectangular shapes. Working with one side at a time, cut diagonal lines to make tree-shaped triangles. (You will have scrap pieces on the ends of the pans. Those are the cook’s treat!)

Repeat on the other side until all the cuts have been made. Let the trees cool completely in the pan. It will look like this:

Once cooled, remove the Rice Krispie trees to a piece of wax paper and insert a small stick pretzel into the bottom of each one. A firm, steady push helps but one or two will probably break on you.

Serve immediately or keep in a covered container at room temperature for up to 4-5 days.