1 cup cold water, divided
3 - 1/4 ounce envelopes unflavored gelatin
2 cups sugar
1 cup corn syrup
1/4 teaspoon salt
A dash of vanilla extract, or any other extracts you'd like to try!
Mix 1/2 cup cold water and the gelatin packets in an electric mixer until blended. Let stand while you make the syrup.
Pour 1/2 c cold water, 1 c corn syrup, and 2 cups sugar into a pan. Bring to a boil, but do not stir! Boil the syrup until it reaches 240 degrees on a candy thermometer, or until it is to "medium pull" consistency (when you make a ball out of a little of the syrup in ice water, and it is firm to push, but not stiff).
Stir in the flavoring(s) you have chosen. You can also add food coloring if you would like.
Pour into a greased 9X13 pan, or into two square cake pans (8X8). Refrigerate until firm. When you cut them into squares, dip the knife in cold water first so the marshmallows don't stick.
You can roll the marshmallow squares in chocolate sprinkles, chopped nuts, toasted coconut, or any other toppings you can think of. I haven't tried them in S'mores, but I'm sure they'd be delicious!