Preheat oven to 325. Butter a 10x15-inch baking sheet (jellyroll pan). Dust with flour and shake out excess. Melt the chocolate and butter in a small saucepan over Very low heat, or in the top of a double boiler. Set aside to cool slightly. Beat the eggs, sugar and vanilla in a bowl with an electric mixer until thick and fluffy. Stir chocolate into the eggs. Add 1 3/4 cups flour and the salt; mix until just combined; do not overmix. Stir in the chopped walnuts, if desired. Bake in center of oven 25-30 minutes or until center of brownies is just set. Allow to cool completely before cutting into squares about 2x2 inches.

Per brownie (without nuts) about 212 calories, 13g fat.