Fudge Swirl Recipe

Prepare pan

Line an 8-inch square baking pan with parchment paper or foil, leaving a 1-inch overhang on two sides for easy removal. Lightly butter the paper or spray with nonstick spray.

In a medium heavy-bottomed saucepan, whisk together granulated sugar and unsweetened cocoa powder until evenly combined.

Add evaporated milk, unsalted butter, and light corn syrup to the saucepan. Place over medium heat and stir constantly until the butter melts and the sugar dissolves.

Bring the mixture to a gentle boil, continue stirring frequently to prevent scorching. Use a candy thermometer and cook until the mixture reaches 234–240°F (soft-ball stage), about 6–10 minutes depending on heat and pot. If you don’t have a thermometer, boil 3–4 minutes after the first steady simmer, stirring continuously.

Remove the pan from heat. Let the mixture cool, undisturbed, for 5 minutes to stop active boiling but remain hot.

Stir in pure vanilla extract and fine salt. Using a sturdy wooden spoon or heavy spatula, beat the mixture vigorously for 2–3 minutes until it becomes thicker and starts to lose glossy shine (this helps set the fudge).

While the fudge base cools for those 5 minutes, make the chocolate swirl. Place the semisweet chocolate chips in a small heatproof bowl.

Heat the heavy cream in the microwave in 15-second bursts or in a small saucepan until just simmering (do not boil). Pour the hot cream over the chocolate chips and let sit 1 minute, then whisk until smooth to form a glossy ganache.

Reserve 2–3 tablespoons of the warm fudge base and fold it into the ganache to slightly loosen and warm it, making the swirl easier to marbelize (optional but helps blend textures).

Pour the fudge base into the prepared pan, spreading it evenly with a spatula. Dollop spoonfuls (about 1–2 tablespoons each) of the chocolate ganache over the top in a grid pattern.

Using a thin knife or skewer, drag lines through the dollops in alternating directions to create a swirl/marble pattern. Do not overmix — you want distinct swirls.

If using, sprinkle coarse sea salt and chopped toasted nuts evenly over the top, pressing lightly so they adhere.

Allow the fudge to cool to room temperature on the counter for about 1 hour, then transfer to the refrigerator to set completely for at least 2–3 hours (or overnight) until firm.

When set, lift the fudge from the pan using the parchment overhang. Place on a cutting board and cut into 1-inch squares with a sharp knife. For clean cuts, wipe the knife between cuts or warm the knife under hot water and dry before slicing.

Store fudge in an airtight container layered with parchment at room temperature for up to 1 week or in the refrigerator for up to 2 weeks. For longer storage, freeze up to 3 months, thaw in refrigerator before serving.