Cook pasta until al dente. Set aside.

Chop bacon into 1 inch pieces and cook until done, then drain the grease. Set aside.

Shred the cheese.

Turn the oven broiler to low.

Add butter to a cast iron skillet, and heat over medium-high heat, until it melts and bubbles.

Whisk in flour, and cook for about 1 minute, then add milk, and bring to a boil.

Remove from heat, then stir in a handful of cheese at a time, until melted.

Add pasta and bacon. Stir until combined.

Sprinkle the breadcrumbs over the top and broil on low for about 6 minutes.

Serve warm.