Bring a large pot of salted water to a boil and add the pasta. While the pasta is cooking, make the sauce.

In the bottom of a deep-sided pot cook the pancetta until crispy. Remove to a plate with a paper towel to drain. Wipe any excess oil from the pot.

Melt the butter in the pot, until it is bubbly being careful not to brown it. Slowly, sprinkle in the flour whisking constantly to form a roux. Continue whisking the roux for a couple of minutes until it is nice and bubbly.

Pour in the milk continuing to whisk and stir until well combined. Add the miso paste and stir to incorporate. Add the mustard, garlic powder, pepper, salt and hot sauce. Bring to a low simmer, then add the cheeses and mix until the sauce is thick and gooey. Lastly, stir in the ½ t. of truffle oil and the pancetta. When the pasta is just under aldente, drain it, reserving about a cup of pasta water then add the pasta to the cheese sauce. If the sauce seems too thick, add a little of the pasta water to thin it out.

NOTE: At this point, because you will have been tasting this and suddenly realize how yummy it is, you will probably want to just go ahead and eat it out of the pot. But you can also add the optional topping and bake it to get some extra texture and crunch. Or you can let it cool in the casserole and refrigerate it. When you are ready to cook it, just remove it about an hour ahead of time and add the topping then before baking.

If you are going with the topping, spread the cooked pasta and sauce into a 9 x 13-inch casserole dish. Combine the topping ingredients and sprinkle them over the top of the casserole. Bake at 375 degrees for about 30 minutes or until the dish is nicely browned over the top.