Line an 8x8-inch pan with parchment paper or nonstick aluminum foil (or grease regular foil with a bit of softened butter).
Place the ⅔ cup evaporated milk, 1⅔ cups granulated sugar, ½ teaspoon salt, and 2 tablespoons butter in a large saucepan over medium heat.
Cook, stirring occasionally, until the mixture comes to a boil.
Continue to cook, stirring constantly so it doesn’t scorch, for 5 minutes.
Stir in the 1½ cups mini marshmallows, 1 package butterscotch chips (11 oz), and 1 teaspoon vanilla extract. Continue to stir until the marshmallows and butterscotch chips have melted.
Stir in the ½ cup chopped toasted pecans.
Pour into the prepared baking dish. Let cool at room temperature until firm (about 4 hours).
Cut into 1-inch squares and serve.
Notes
Toasted pecans make the tastiest fudge! I recommend purchasing toasted pecans, or you can toast them yourself. If you want to swap them out for something else, try chopped walnuts or toffee bits. Top tips:
Prepare the pan first, before making the fudge! The fudge sets up quickly and this ensures the creamiest results.
Stir the mixture constantly once it boils. The evaporated milk has a tendency to scorch.
Give the fudge about 4 hours at room temperature to set up. You can speed it up in the refrigerator, but I find that it's easiest to slice at room temperature.
Storage information: the fudge will keep for several weeks either at room temperature or in the refrigerator in a covered container.Freezing: you can freeze the fudge for up to 3 months. Defrost at room temperature.