- Nonstick vegetable oil spray
- 2¼ cups sugar
- 1 cup heavy cream
- 3 tablespoons light corn syrup
- ½ teaspoon kosher salt
- 6 ounces unsweetened chocolate, chopped
- 4 tablespoons butter, cut into pieces
- 2 teaspoons vanilla extract
- 1 teaspoon peppermint flavoring or extract or ¼ teaspoon peppermint oil
- 2 ounces soft peppermint puff candies, finely crushed
- A candy thermometer
Line an 8x8" baking dish with foil, pressing into edges. Lightly coat with nonstick spray. Heat sugar, cream, corn syrup, salt, and 2 Tbsp. water in a medium saucepan over medium, stirring, until sugar dissolves. Add chocolate and stir until melted and mixture is smooth, then bring to a boil. Fit saucepan with candy thermometer and increase heat to medium-high. Cook, brushing down sides of saucepan with a wet pastry brush as needed to dissolve sugar crystals, until thermometer registers 238°.
Immediately pour mixture into a large bowl (do not scrape bottom or sides of pot). Dot top of mixture with butter; do not stir. Rinse thermometer, removing any sugar crystals, pat dry, and fit on bowl. Let mixture sit until thermometer registers 110°, 30–45 minutes.
Remove thermometer. Add vanilla extract and peppermint flavoring to mixture and beat with a hand mixer on high speed until mixture is light and thick like frosting and has lost its high gloss (will still have a slight sheen), about 4 minutes.
Scrape into prepared pan; smooth surface, then top with peppermint candies, pressing gently into surface. Cover with plastic and let fudge sit at room temperature until set, at least 4 hours.
Using foil, remove fudge from pan, peel away foil, and cut fudge into a 6x6 grid to make 36 squares.
Fudge can be made 3 days ahead. Keep stored at room temperature.
Fudge without candy canes can be kept chilled in a sealed container for up to 2 weeks
If fudge doesn't set it can be boiled again after adding two tablespoons of cream to the mixture. Remove candy canes if possible first.