Beat egg with buttermilk and stir in other ingredients. James Beard says that this is the best onion-ring batter he has ever found. It can also be used with most veggies; Beard suggests artichoke hearts, asparagus, broccoli flowerets, Brussels sprouts, eggplant fingers or slices, fiddleheads, green beans, mushrooms, pepper strips, snap peas, snow peas, spinach leaves, sunchokes, zucchini strands.