For one 9in x 13in pans worth:
¾ cup cocoa powder
2 ¼ cup sugar
2 teaspoons vanilla
1 1/3 cup gluten-free flour (used Bette Hagmans mix plus Xanthan Gum)
1 cup chopped nuts (if desired)
½ teaspoon baking powder
¼ teaspoon salt
Preheat oven to 325F Grease (not oil) and lightly cocoa (instead of flour) 9x13 pan. In large sauce pan, melt margarine/butter with cocoa over low heat, stirring constantly (actually, I just put the cocoa and butter in a bowl, stick it in the microwave for a couple of minutes, until the butter is melted. Stir with a fork until its mostly smooth. Remove from heat and cool slightly. Blend in sugar. Beat in eggs, one a time. Stir in remaining ingredients. Spread in prepared pan.
Bake at 325F and check after 20-25 minutes (I use a stoneware pan and it takes about 10 minutes longer than in a metal pan). I consider them done when whatever is stuck in the middle to check for doneness (toothpick, butter-knife, whatevers handy) comes up a bit moist, but not with a great deal of chocolate adhering to it. Im aiming for a slightly gooey middle and somewhat cake-like edges. Its safe to say that they will not be done before 20 minutes unless your oven really cooks on the hot side.