Spray a 12 by 17 inch rimmed baking sheet with cooking spray. Line the baking sheet with a piece of parchment paper and spray the parchment paper. Set aside. *Note if you don’t have a 12×17 inch pan, you can use a another similar sized pan, the marshmallows just may be thicker.
In a mixing bowl, add 1/3 cup cold water and sprinkle the gelatin evenly over the water. Allow the gelatin to soften, about 5 minutes.
In a medium saucepan, combine the sugar, corn syrup, salt and 1/3 cup water. Cover the pan and bring the mixture to a boil. Once boiling, remove the lid and stick in a candy thermometer. Stir the mixture occasionally until it reaches 238 degrees (the soft-ball stage), about 5 minutes.
While beating the mixture on low, slowly pour the syrup in a steady stream down the side of the bowl that has the gelatin in it.
Increase the speed of the mixer gradually to high and beat until the mixture is thick and almost tripled in volume, about 12 minutes. Add in the peppermint extract and green food coloring, beat for 1 more minute or until the color is even.
Add in the mini chocolate chips and stir the mixture by hand.
Pour the marshmallow mixture onto the prepared baking sheet and even the mixture using a spatula sprayed with non-stick cooking spray. Let the marshmallows stand at room temperature, uncovered overnight.
The following day, use a shamrock shaped cookie cutter to cut out as many marshmallow as possible. If the marshmallows are too sticky, spray the cookie cutter with non-stick spray. Store the marshmallows in an air tight container.
These marshmallows aren’t super thick, they are made to be thinner.