I have made hundreds of these brownies over the past 20 years. Follow the instructions exactly. My favorite baking tools are 1/2 sheet pans with a riser and parchment. This recipe fills a 1/2 sheet pan perfectly. A 1/2 sheet pan with riser measures 16 inches by 11.5 inches. If you use a 9 inch by 12 inch cake pan divide this recipe in half. I like 1/2 sheet pans with a riser because you can remove the riser after the cake is cooled and easily cut it. If you use a cake pan you can make a sling of parchment or aluminum foil to easily remove your masterpiece.
1 pound of butter in a double boiler with 12 ounces of unsweetened chocolate.
When melted remove from double boiler and whisk in 8 eggs. The mixture will thicken. Then add 2 pounds of natural sugar. This will cool the mixture. Next add your flour mixture which is 5 cups flour, 3 tsp baking powder and 2 tsp salt. You can also add 1 cup chocolate chips and 1 cup nuts. Combine the two mixtures and layer into your pan. Bake in a preheated oven @ 350 degrees for 20 to 25 minutes. Top should be firm and have some color. A tooth pick with come out clean. It's temperature will be 190 degrees.