1) Cook macaroni according to package instructions and set aside.

2) Cut up bacon into 1/4 inch cubes and cook in cast iron skillet over medium-high heat until very crispy and browned.  If bacon appears dry, drizzle with a bit of olive oil.

3) Remove bacon from pan and add onions and crushed peppers or red pepper flakes.  Cook until onions are soft, about 5 minutes, stirring continuously.  Remove onion mixture and combine with bacon.

Do not wash the skillet, but set it aside for later.

4) In a medium saucepan, melt butter and whisk in flour over medium heat.  Cook until the roux is a light brown mixture, about 5 minutes.  Continue to whisk and slowly pour in milk.  Once all the milk is incorporated, whisk until smooth and turn the heat down to low.

5) Whisk in shredded cheeses and a pinch of salt and pepper to taste.

6) Combine cheese sauce with elbow macaroni and stir in bacon mixture.  Pour the macaroni and cheese back into the cast iron skillet and top with grated Parmesan and/or bread crumbs.

7) Bake at 400 degrees for 30 minutes until cheese is browned.

8) Cool for 10 minutes before serving.