Ingredients
Vegetable-oil cooking spray, for pan
4 tablespoons unsalted butter
3 packed cups mini marshmallows, or cut-up regular marshmallows (6 ounces)
1 1/2 cups sugar
1/2 cup whole milk
1/4 teaspoon kosher salt
1 teaspoon pure vanilla extract
12 ounces bittersweet chocolate, coarsely chopped
1 cup pulverized peppermint candies; or finely chopped toasted walnuts; or finely chopped pistachios; or ground freeze-dried raspberries (or a combination of all four)
Preparation
Lightly spray a 9-by-9-inch cake pan with cooking spray. Line with 2 crisscrossed pieces of parchment, leaving a 2-inch overhang. Spray parchment. In a saucepan, combine butter, marshmallows, sugar, milk, and salt.
Cook over medium-high heat, stirring frequently, until marshmallows have melted, 6 to 7 minutes. Stir in vanilla. Remove from heat; stir in chocolate until melted. Pour mixture into prepared pan. Let cool 30 minutes, then refrigerate until set, at least 1 hour and up to 3 days.
Using overhang, lift fudge onto a cutting board; cut into 1-inch squares. With rubber-gloved hands, to prevent fudge from becoming too slippery and messy, roll into balls (if mixture is very cold, it may crumble a bit; just let it warm slightly first), then roll in desired toppings as you go. Refrigerate until firm, 1 hour. (To make ahead, place balls in a single layer on a parchment-lined baking sheet, wrap in plastic wrap, and refrigerate up to 3 days.)
