1 stick unsalted butter plus extra for greasing
4 ounces bittersweet chocolate
2 1/2 large eggs – (to halve an egg, crack 1 and use 2 tablespoons)
1 1/2 cups granulated sugar
1/2 tablespoon vanilla
1/2 teaspoon salt
3/4 cups flour
1 cup toasted, chopped pecans or walnuts
Preheat oven to 375 (350 for glass pan) degrees. Line an 8 inch square metal pan with foil and butter the foil.
Melt the butter in a heavy saucepan over medium heat. Add chocolate, turn off heat, and stir until melted from the residual heat. Let it cool for about 5 minutes.
Beat the eggs and sugar until light and fluffy, 5 to 7 minutes. Beat in the melted chocolate (which should be slightly warm, but not piping hot at this point), vanilla and the salt. By hand stir in the flour until it is almost combined, then add the nuts and continue stirring gently until all flour disappears.
Pour the batter into the prepared pan, smooth to the edges, and bake in the center of the oven until puffed and almost set, about 38 to 40 minutes.