Begin cooking your pasta according to package instructions. Do not over-cook, in fact, for best results cook one minute less than indicated time. Once finished, drain, drizzle with a tiny bit of olive oil and toss to coat so the noodles don't stick together while sitting.
Meanwhile, melt butter in a 10" cast iron pan² over medium heat. Once it has melted, add flour and whisk until smooth and no lumps remain..
Add milk and spices (salt, pepper, garlic powder, onion powder, and ground mustard), stir well and bring to a boil. You may notice that the milk and butter will separate -- continue to heat, stirring frequently, until the milk is heated and they combine
Once mixture comes to a boil, reduce heat, bring to a simmer, and stir frequently until mixture is thickened.
Reduce heat to low and add cheddar and mozzarella cheese. Stir until cheeses are melted and mixture is smooth.
Add cooked, drained pasta noodles and stir until well coated by the sauce.
Set aside while you prepare your Panko topping.
Combine butter and olive oil in a small saucepan over medium heat. Heat, stirring occasionally, until melted.
Add panko and stir well until the butter and oil has been mostly absorbed. Continue to stir until panko is lightly toasted and turns a light-medium brown color
Sprinkle toasted panko evenly over mac and cheese.
Transfer to oven and bake uncovered on 350F (175C) for 15 minutes.
Garnish with parsley, if desired, and serve.
¹You may substitute another type of shredded cheese for all or part of this -- Colby, Monterey Jack, and Gruyere, would all work well. I personally use half sharp cheddar and half white cheddar for mine! I also recommend buying your own block of cheese and grating it yourself to ensure that the cheese melts properly, please see my post for more information on pre-shredded vs block cheese.²If you don't have a 10" cast iron pot, then prepare your macaroni and cheese according to these instructions and then transfer to a lightly buttered 9x9 square pan or 1.5qt baking dish before topping with panko and baking.