Brown ground beef, drain; add Worcestershire sauce, black pepper, seasoned salt, garlic powder, and mustard to ground beef and cook for an additional 2 minutes.
Add 1 tbsp butter and sliced onions to pan and saute until onions just start becoming limp.
Spread ¼ cup ground beef mixture down the center of one tortilla, top with onion, roll it to contain the filling, and place seam side down in 9×13 greased casserole dish. Repeat with remaining tortillas.
Fry bacon, crumble it, and set aside.
Melt remaining butter in a saucepan, stir in flour and cook for two minutes. Whisk in milk and one cup of cheese; stir until cheese is melted.
Pour cheese sauce over enchiladas; sprinkle remaining cheese and bacon over enchiladas.