4 sticks salted butter 8 squares (8 oz) unsweetened chocolate 8 eggs 4 c. sugar A little more than 2 c. potato starch A little less than 2 c. matzo cake meal 2 teasp. vanilla Powdered sugar
In a 5 quart sauce pot, melt butter and chocolate over low heat. (Put the chocolate on top of the sticks of butter.) Stir with wooden spoon until fully melted then remove from heat. When cooled a little, mix in sugar. Then beat in the eggs by hand, 1 at a time, until the mixture is glossy. Don't overbeat. Mix in matzo cake meal and potato starch. Mix in vanilla.
Pour into a very lightly greased jelly roll pan (the size of a large cookie sheet but needs to have sides that come up) and bake at 305º for 45 min. Brownies should be very fudgy but a tester (toothpick) should come out fairly clean. Try not to overbake so the center is fully cooked; but try not to underbake so the center is not cooked through.
When the pan has cooled (best to let it sit overnight), cut the brownies into small rectangles with a sharp spatula, turn upside down and sprinkle with powdered sugar.