Buttermilk is an important ingredient in this recipe. If you don’t have any on hand, or don’t want to buy a quart of buttermilk just to use the quantity needed here, an easy substitute is to make your own using just under a cup of regular milk and adding a tablespoon of either white vinegar or lemon juice to it. Stir together, let it sit for 5 minutes and then use as you would buttermilk in your recipe.