1. To make brownies: Preheat oven to 350-degrees F.
2. Butter and flour 8-inch square baking pan or line pan with buttered and floured parchment paper.
3. Sift together first 4 ingredients (flour- salt). Repeat (sifted twice). Set aside.
4. Cream butter with sugar and vanilla until light.
5. Beat in eggs one at a time.
6. Add corn syrup.
7. Add dry ingredients, blending well. Stir in walnuts, if using.
8. Spoon batter (batter will be very thick) into prepared pan, smoothing with plastic spatula or knife.
9. Bake for 30-35 minutes or until toothpick tests clean.
10. Cool while making frosting.
11. To make frosting: Melt chocolate and butter in double boiler over simmering water or in microwave. Stir in sugar, water and vanilla.
12. Spread frosting over brownie. Sprinkle with walnuts, if desired.
13. Let stand until frosting sets and then cut into 8 squares.