COOKING SURFACE: When doubling or tripling a recipe, expect all the ingredients to take longer to cook. In large recipes the amount of ingredient surface exposed to direct heat is less than with smaller recipes where a greater percentage of  ingredient surface is exposed to the heat, thereby cooking the ingredients faster. Any time you have food setting on top of food, or deep pots of soups or sauces, cooking times of all ingredients and throughout each step of the cooking process lengthens.