Beacon Hill Brownies

1 package unsweetened chocolate (8 squares)
1 cup butter or margarine
5 eggs
3 cups sugar
1 Tbsp. vanilla
1 1/2 cups unsifted flour
2 cups coarsely chopped walnuts or pecans (optional)

Melt chocolate and butter in saucepan over very low heat, stirring constantly.  Cool slightly.   Beat eggs, sugar, and vanilla in large mixer bowl on high speed for 10 minutes.  Blend in chocolate mixture on low speed.  Add flour, beating just to blend.  Stir in nuts.  Spread in greased 13 x 9 inch pan.  Bake at 375 degrees for 35 to 40 minutes.  Do not over bake. Cool in pan; cut into squares.