Martha and California candy maker Kimberly Reiner make fudge-covered marshmallows. Part 1.
Lightly spray a 9-by-13-inch glass baking dish with nonstick cooking spray. Sprinkle gelatin over a small bowl filled with 1/2 cup cold water; let stand to soften.
In a heavy bottomed saucepan, mix together sugar, corn syrup, hot water, and salt. Place over medium heat and cook, stirring, until sugar has dissolved. Continue cooking, without stirring, until mixture reaches the soft-ball stage, about 240 degrees on a candy thermometer. Remove from heat and add gelatin mixture; set aside.
In the bowl of an electric mixer fitted with the whisk attachment, beat egg whites on high speed until stiff peaks form. With the mixer running, slowly add sugar mixture. Add vanilla and continue beating for 10 minutes until the mixture looks like marshmallow.
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.
Line a baking sheet with parchment paper; set aside. Working with 1 marshmallow at a time, insert skewer into a marshmallow and dip in fudge until coated on all sides, removing any excess from bottom of marshmallow; place on prepared baking sheet. Repeat process with remaining marshmallows (you will have some marshmallows left over). Let chocolate covered marshmallows stand at room temperature overnight before serving or transferring to an airtight container for up to 3 days.