Position rack in middle of oven. Heat oven to 350 degrees F. Line 13 x 9 x 2- inch baking pan with foil; grease foil.
Bring saucepan of water to a boil and turn off heat. Combine butter and chocolate in heatproof bowl and set over the saucepan of hot water. Stir occasionally until melted.
Whisk eggs together in a large bowl; then whisk in salt, sugars and vanilla. Stir in melted chocolate-butter mixture; fold in flour. Pour batter into prepared pan, spreading evenly.
Bake in 350 degree F oven for about 45 minutes, until top has formed a shiny crust and cake is moderately firm. Cool in pan on rack. Wrap pan in plastic wrap and keep at room temperature or refrigerated for a day.
To cut brownies, unmold onto board; remove foil; replace with another board. Turn right side up. Cut into 2-inch squares. Serve with ice cream, sauce and cherries, if desired. Makes about 24 (2-inch) brownies.