Heat 1 12″ -2″ oil in a deep 12″ skillet over medium-high heat until temperature registers 350°. Whisk 1 egg yolk, 1 cup cold water, and 1/4 cup ice cubes in a bowl. Add 1 1/2 cups flour and seasonings of choice, to taste; gently stir until barely combined (batter should be lumpy, not smooth). It is important to keep batter as cold as possible. Working in batches, dredge mushrooms (recipe is for 1 pound total) in additional 1/2 cup flour, and dip into batter. Drop into to oil, and fry, flipping once, until crisp, 2-4 minutes. Using a slotted spoon, transfer to paper towels to drain and season with salt and pepper. Serve with favorite dipping sauce or mix some up, we use: 1/4 cup mirin, 1/4 cup soy sauce, 1/2 cup brown sugar and 1 T fresh minced ginger. Stir over low-medium heat until well mixed.