Prep your pan. Line an 8x8-inch baking pan with parchment, leaving overhang on two sides for easy lifting. Lightly butter the parchment.

Toast the walnuts. In a dry skillet over medium heat, toast chopped walnuts for 3–4 minutes, stirring often, until fragrant. Let cool.

Combine the base. In a medium, heavy-bottomed saucepan, add sugar, maple syrup, heavy cream, butter, and salt. If using, stir in the corn syrup. Set over medium heat and stir gently until the sugar dissolves and the butter melts.

Cook without stirring. Bring the mixture to a gentle boil. Reduce heat to maintain a steady simmer. Cook until it reaches 236–238°F (soft-ball stage), about 8–12 minutes. If you don’t have a thermometer, drop a bit into cold water; it should form a soft, pliable ball.

Cool before beating. Remove from heat and let it sit, undisturbed, for 10–12 minutes until the temperature drops to about 110–120°F. This rest helps the texture turn creamy instead of grainy.

Beat to thicken. Add vanilla (and maple extract if using). Beat with a wooden spoon or hand mixer on low until the mixture loses its gloss and thickens. This takes 3–6 minutes. You want it pourable but not shiny.

Fold in walnuts. Stir in the toasted walnuts, reserving a few for topping if you like.

Pour and smooth. Scrape the fudge into the prepared pan, smooth the top, and sprinkle remaining walnuts over. Gently press them in so they stick.

Set and slice. Let sit at cool room temperature until firm, 2–4 hours. For clean cuts, refrigerate for 30 minutes before slicing. Lift with the parchment and cut into 1-inch squares with a sharp knife.