Salted Marshmallow Walnut Fudge

16 ounces dark chocolate, preferably about 70 percent, coarsely chopped

1 teaspoon table salt

One 14-ounce can sweetened condensed milk

1 tablespoon pure vanilla extract

2 cups toasted walnuts, coarsely chopped (see note)

3 cups mini marshmallows

Flaky sea salt, for sprinkling

Turbinado sugar, for sprinkling

Grease an 8-inch-square baking pan with cooking oil spray, then line it with wax paper, leaving some overhang on the sides to help you extract the slab of fudge later.

Fill a medium saucepan with a few inches of water; place over medium-low heat. Place the chocolate in a heatproof bowl that can sit over the saucepan (to create a double boiler; the bowl should be large enough to eventually contain all the ingredients). Once the chocolate starts to melt, use a flexible spatula to stir constantly until smooth.

Add the table salt, sweetened condensed milk and vanilla extract; increase the heat to medium or medium-high, stirring to incorporate for about a minute or two. The chocolate may seize up a bit, but keep stirring. Once the mixture is smooth, stir for about 1 minute more, then remove from the heat.

Add the walnuts and marshmallows; stir or fold them in until evenly distributed (the marshmallows will not melt). Transfer the fudge mixture to the prepared pan. Cover with wax paper or plastic wrap and flatten with your hands, then uncover just long enough to sprinkle the surface with flaky sea salt and turbinado sugar.

Re-cover and refrigerate for 1 to 2 hours, until firm. Use the waxed-paper overhang to transfer the fudge to a cutting board, then use a sharp knife to cut the slab into 36 equal pieces.

Note: Toast the walnuts by spreading them on a baking sheet and baking in a 350-degree oven, shaking the sheet occasionally, for 10 to 13 minutes until fragrant and nicely browned. Watch carefully; nuts can burn quickly. Cool completely before using.

36 servings; pieces makes one 8-inch pan

Nutrition | Calories: 150; Total Fat: 9 g; Saturated Fat: 4 g; Cholesterol: 5 mg; Sodium: 100 mg; Total Carbohydrates: 18 g; Dietary Fiber: 1 g; Sugars: 15 g; Protein: 3 g.

Adapted from "The Vintage Baker: More Than 50 Recipes From Butterscotch Pecan Curls to Sour Cream Jumbles," by Jessie Sheehan (Chronicle Books, 2018).