To prepare beer batter: Combine cornstarch, flour, garlic salt, paprika, salt and pepper. Stir in beer; mix well. Set aside.
To prepare seasoned flour: Combine flour, paprika, garlic powder, pepper and cayenne. Mix well.
To prepare chili sauce: Combine mayonnaise, sour cream, chili sauce and cayenne. Mix well. Refrigerate until ready to serve.
To prepare onions: Cut about 3/4 inch off top of each onion. Peel onions. Cut each into 12 to 16 vertical wedges, but do not cut through bottom (root end) of onions. Remove about 1 inch of "petals" from center of onion. Soak cut onions in ice water for 10 to 15 minutes. If onion petals do not separate and "bloom," cut petals slightly deeper.
Dip cut onion in seasoned flour. Remove excess by shaking. Dip into batter and remove excess by gently shaking. Separate "petals" to coat thoroughly with beer batter. Gently place onion in fryer basket and deep-fat fry at 375 degrees for 1 to 1 1/2 minutes. Turn over; fry an additional 1 to 1 1/2 minutes longer until golden brown. Repeat with remaining onion.
Drain on paper towels. Place onion upright in shallow bowl. Place one cup of creamy chili sauce in center of each onion. Serve.