I hope you give these a try, it makes you want to never have store bought ones again. Last year I covered some in chocolate and those are pretty tasty too. Be creative and add some flavorings or food coloring in too.
2 tablespoons plus 1/2 teaspoon unflavored gelatin
2 cups sugar
1/2 cup light corn syrup
1/2 cup hot water
1/4 teaspoon salt
2 large egg whites
1/2 teaspoon pure vanilla extract
1 cup cornstarch (I used powdered sugar)
Transfer marshmallow mixture to prepared baking dish and spread evenly. Spray a piece of parchment paper with nonstick cooking spray and cover marshmallow. Let stand overnight.
Remove parchment paper and invert marshmallow onto work surface. Trim 1/4-inch from edges of marshmallow. Cut marshmallows into 1 1/2-inch squares. Pour cornstarch in a bowl; working in batches, gently add marshmallows and toss to coat.
I then added a little extra powdered sugar in the containers I was giving away because the marshmallows will soak up the sugar and get sticky.