The recipe says you can use butter or margarine, but it works much better with butter. But if all you have is margarine, it comes out ok with that too. What I notice when I use margarine is that my brownies get bumps, and with butter they are nice and flat.
The recipe this was taken from was written when unsweetened chocolate was sold in boxes of eight squares. Today they are not always sold in exactly the same format. However, they are still sold in eight-ounce (225 gram) boxes so, if they are not in eight one-ounce portions, just use half the box.
1 cup butter or margarine
4 squares (4 ounces) unsweetened chocolate (half a box)
2 cups white sugar
1 cup flour
1 teaspoon vanilla
½ teaspoon salt
Chopped nuts (optional)
In a large medium sized saucepan, melt the chocolate and butter or margarine over medium high heat, stirring often with a whisk. When the chocolate and butter have melted, remove from heat and place on the counter on a potholder. Add the vanilla. Add the sugar and stir well with the whisk. Add the eggs one egg at a time, stirring vigorously after the addition of each egg. After adding all four eggs, add the flour and the salt and stir vigorously again. Add nuts if you are nutty. Grease and flour a 9 inch by 13-inch pan. Bake at 350° for about 30 minutes. Spin the pan around every 5 minutes or so, so they will cook evenly. You will know it is cooked when it is “bouncy” to the touch, not soft. You can also tell it is done when you put in a toothpick and it comes out dry.