1 1/3 cups flour mixed with 1 teaspoon salt and pinch pepper
2 stiffly beaten egg whites, optional
Combine yolks with oil and beer. Gradually stir this into flour (it should be thick enough to stick to the food) and beat until very smooth with a few swift strokes. Rest batter, covered, in refrigerator for 3 hours at least so it ferments a bit. Get oil to right temperature. Beat egg whites until stiff and fold into batter. Dip the onions or mushrooms in the batter and fry.