I have a brownie recipe I have used for years. In recent years, I find that I sometimes get batches that have huge areas of bubbled-up brownie and are inedible. I honestly do not know what I am doing differnetly when this happens. I cream 2 cups of sugar with 2 sticks of butter and add 4 eggs and 1 tsp vanilla. Then I add a cup of flour with 5-6 Tbsps of cocoa, alternating with 4 tblsp of milk. Most of the time I get a wonderful pan of brownies, but sometimes, I get a pan of brownies with huge areas that are giant domes scattered throughout the pan. I am not mixing them enough or am I beating them too hard? I just do not see what I am doing differently when this happens. Thanks for your help.