Heat oil in a wide deep skillet and saute onions and garlic until soft. Season with salt and pepper.
Combine flour, chili powder, paprika, salt, minced onion, cumin, cayenne, garlic powder and oregano and add to skillet (or use 2 envelopes of taco seasoning). Cook, stirring, until well mixed, about 2 minutes.
Add ground beef, breaking up with a spoon, and cook until beef is browned. Stir in tomatoes and their juices, corn, and beans and cook until heated through.
Stack tortillas on a microwave safe plate and cover with a damp paper towel. Microwave on high power for 60 seconds to warm and soften tortillas.
Butter a 10x15x2 casserole and line the bottom with 6 of the tortillas. Cover with 1/2 of the meat mixture and 1/2 of the shredded cheeses. Repeat with remaining tortillas, meat and cheese.
Bake 25 - 30 minutes at 350*. Let stand 5 - 10 minutes.
Meanwhile, combine chipotle and adobo with sour cream. For moderate heat, remove seeds and pith of chiles.
Cut casserole into 6 - 8 servings. Top each serving with shredded lettuce, olives, guacamole, and adobo sour cream. Dig in!