Preheat oven to 325 degrees. Grease and lightly flour two 8 x 8" pans or one 13 x 9" pan. The single pan will give you a higher brownie which makes great little squares. Another option to greasing and flouring is lining the pan with aluminum foil and greasing that lightly. When you pull it out, the pan is clean and you peel the foil right off before cutting. It provides great "walls" for the fudge to settle on top of the brownies.
Melt chocolate in a saucepan. Add butter and stir to blend. In a mixing bowl, combine eggs, sugar, and vanilla extract. Stir in chocolate mixture, add flour and mix well.
Spread batter in the prepared pans and bake in over for approx. 40 minutes. Check brownies before baking time--if they pull away from the side of the pan, they are done. Remove from oven immediately and cool slightly.
Chop up the chocolate and combine with sugar, salt, cream, and corn syrup in a heavy saucepan. Over very low heat, stir until melted and smooth. Increase heat to medium high and cook, stirring occasionally until you reach "soft-ball stage" on a candy thermometer. Remove pan from heat, add butter, and cool slightly. Add vanilla extract and start to heat vigorously. Do not let get too thick but a nice pouring consistency. Pour over cooled brownies, let set, and cut into desired shapes.