Preheat oven to 325 degrees. Lightly butter an 8-inch square baking dish, then line with two pieces of buttered parchment paper that have been cut to fit the pan crosswise. Flour the pan.

In a small mixing bowl, stir together the flour, salt, and nuts (if using). Set aside.

Melt the chocolate and butter in the top of a double boiler over simmering water just until melted. Alternatively, place chocolate and butter in a large microwave-safe bowl and melt in the microwave.

Remove from heat and stir in the sugar. Set aside and let cool for 3 to 4 minutes (so you don’t cook the eggs). Stir in vanilla and eggs until well blended. Finally, stir in the flour and nut mixture just until combined.

Pour batter evenly into the prepared pan and bake for about 35 to 40 minutes, or until a toothpick inserted in the center comes out clean.

Remove from oven and let brownies cool completely in the pan on a wire rack.

To serve, pull up the parchment paper and gently remove the brownies from the pan. Remove the paper and place brownies on a cutting board. Sift powdered sugar over the top. Cut with a sharp knife, and wipe the knife clean with a damp paper towel between cuts. Can also refrigerate brownies for at least 30 minutes to make cutting easier.