Heat oil in a large, deep, fat-fryer or a deep, heavy kettle to 375? F. Preheat oven to 200? F.
Prepare the onions: Peel them and slice off top to make a flat surface. Cut onion into quarters from top, to within 1/2-inch of the root base. Then cut the quarters into quarters, again being careful not to cut through the root base. (It is easiest to cut the smaller segments if you flip the onion over after first quartering it. Then insert the knife into the onion 1/2 inch below the root base and slice downward, holding the onion steady.) Turn onions back over and gently spread slices apart to form petals. Set aside.
Make the seasoned flour: In a medium bowl, mix flour, paprika, garlic powder, black pepper, and cayenne pepper; set aside.
Make the batter: In a large bowl, thoroughly mix cornstarch, flour, garlic salt, paprika, salt, and black pepper. Whisk in beer or ale; set aside.
Flour and batter onions one at a time. Dip onions in seasoned flour, shaking to remove excess. Onions should be thoroughly, but lightly, floured. Then dip onions in batter, making sure they are thoroughly covered. Drain petal-side down on slotted spoon or spatula to let excess batter drip out.
Using a long-handled slotted spoon or strainer, and wearing oven mitts to protect against spatters, lower coated onion gradually into the heated oil, with onion base-side down. Fry 3 minutes, or until light golden. (Fry one onion at a time so temperature of oil doesn't drop too much.) Using the long-handled slotted spoon or strainer, remove the onion from the oil and place on paper towels. Cool slightly.
Using a knife and fork, carefully spread the petals as much as possible. With the strainer, lower the onion back into the hot oil, this time with base-side up, and petals down. Deep-fry another 3 minutes, or until golden brown. Remove to drain on paper towels, with the petals pointing up. Repeat with remaining onions. Keep the cooked onions warm in a 200 degree F oven while frying the others.
Meanwhile, make the chili sauce: In a medium bowl, mix mayonnaise, chili sauce and cayenne pepper.
Serve onions on a platter, either with a small cup of the Creamy Chili Sauce in the middle of each onion or with the sauce on the side.