In a medium saucepan start water boiling for macaroni noodles.
In a large saucepan or 3.5 qt. dutch oven melt butter until it starts to bubble.
Whisk flour into butter a little at a time until a roux is formed.
Cook the roux over medium - low heat whisking frequently until the color starts to darken just a little and it smells less like butter and flour and more toasty
Whisk the white pepper and mustard powder into the roux until roux is homogenous
While constantly whisking, slowly add the warmed milk to the flour (if you forgot to warm the milk, no worries, using a microwave safe vessel give it 1-2 30 second rounds in the microwave until it feels warm, do not allow it to boil) and let the mixture cook without boiling until it starts to thicken. It should be thick enough that when you dip a wood spoon in it the mixture coats the back of the spoon.
Your water should be boiling now, if so add the macaroni noodles if not, wait for it to boil and add the noodles. Cook for 2 minutes less than package instructions. Once noodles are cooked, drain noodles and set aside.
When the sauce is thickened, turn the heat off and slowly add all of the shredded cheese, about 1/2 cup at a time, stirring continuously until smooth before adding the next 1/2 cup of cheese.
Stir in cooked macaroni, taste and add salt and/or pepper if necessary, and the bacon if you haven't already eaten it all.
If you prefer a super creamy mac best eaten with a spoon your mac is ready, enjoy!
If you prefer a hearty, casserole style mac best eaten with a fork follow the next three steps.
If your sauce pan isn't oven safe, transfer the mac to a greased, oven safe casserole dish.
Melt 2 tablespoons of butter in a microwave safe bowl, then add the breadcrumbs and parmesan cheese and stir together with a fork. It will take a little bit to get it all evenly combined, but it will happen.
Sprinkle topping over top of the mac evenly.
Bake in a 350 degree F oven for 15-20 minutes in the oven until the top is toasty and the edges of the mac are bubbling.