Heat oven to 400 degrees F. Spray 2 cast iron straight-sided muffin pans (6 cups each) with no-stick cooking spray. Stir together cornbread mix, flour, milk, sour cream, and egg in medium bowl until well blended. Stir in chives, bacon, and cheese. Fill prepared muffin pans 3/4 full. Bake 10 to 12 minutes or until golden brown. (Any remaining batter may be made into additional muffins.)
Melt butter in a 12-inch Lodge cast iron skillet over medium-low heat. Add onions. Cook until onions are translucent, 8 to 10 minutes. Remove onions and set aside.
Combine ground chuck, egg, bread crumbs, garlic, salt, and pepper in large bowl. Blend well. Divide into 12 equal portions. Pat out into thin burgers. Cook in skillet over medium to medium-high heat until done. Top each burger with slice of cheese.
Combine mayonnaise, chipotle pepper and adobo sauce. Slice cornbread to make buns. Spread thin layer of chipotle mayo on top and bottom. Place burger on bottom halves. Top with onions. Place top on burger.