Time: 1 hour, plus several hours’ resting


1 1/2 cups unsalted butter, plus more for greasing pan
1 1/2 cups walnut halves (optional)
9 ounces unsweetened chocolate, chopped or broken into small pieces
3 large eggs
1 teaspoon salt
2 3/4 cups sugar
1 tablespoon vanilla extract
1 1/2 cups unbleached all-purpose flour.

1. Heat oven to 350 degrees. Butter a 13-by-9-inch glass baking pan. If using walnuts, spread on a baking sheet and toast in oven until fragrant and lightly browned, 8 to 10 minutes. Let cool.

2. Melt butter in a small saucepan over low heat. Remove from heat, add chocolate, and cover pan until chocolate is melted, about 10 minutes. In a mixing bowl, whisk the eggs, salt, sugar and vanilla just until thick, creamy and beginning to lighten in color.

3. Whisk the butter and chocolate until smooth, then mix into the sugar-egg mixture just until well combined. Using a spatula, fold in the flour, using as few strokes as possible, until it disappears. Fold in the walnuts, if using. Spread the batter evenly in the baking pan.

4. Bake for 25 to 30 minutes, checking after 22 minutes to avoid over-baking. When the tip of a knife inserted in the center comes out with moist crumbs, but not liquid, remove brownies from the oven. Allow to cool to room temperature, then cover and leave in the pan for several hours or overnight before cutting into squares. Store in an airtight container.