Sift together the powdered sugar and cornstarch in a small bowl.
Grease a 9x13 pan. Add 1 tsp of the powdered sugar mixture to the 9x13 and move around until sides and bottom are coated. Put aside.
In your large bowl add 1/2 cup water and sprinkle on the gelatin. Let that sit for 10 minutes.
While that is sitting, in a saucepan with a candy thermometer combine the sugar, corn syrup, salt and the last 1/4 cup of water. Heat it until the sugar has dissolved on medium heat.
Turn up to medium high heat and bring to hard boil for 1 minute, and once thermometer reaches 240F degrees.
In the bowl of gelatin and whisk, slowly add the boiling mixture. Turn the mixer on high for 5 minutes.
Stop and add about 10 drops of the green or until it is mint green in color.
Start mixing again for another 3 minutes or until there is stiff peaks.
Add the peppermint and vanilla. Mix another minute. Fold in your mini chocolate chips.
Pour the mixture into the pan and smooth. Sprinkle on the remaining chocolate chips. Cover with plastic wrap.
Let it sit for 3-4 hours. Take a knife around the edges then invert onto cutting board.
Cut the marshmallows in 2 inch squares. Enjoy.