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 ΒΌ 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.