Bring a large pot of water to a boil and salt generously. Cook the pasta until it is al dente, about 7-10 minutes.
While the noodles are cooking, preheat the oven to 375ºF. Spray a 9x13-inch casserole dish with nonstick cooking spray.
Heat the half and half and milk in a pot over medium heat. Don’t boil it, you just want it warmed through.
In a large skillet, melt the butter over medium heat. Add in the flour and whisk to combine. Cook, whisking constantly, for about 2 minutes, until the flour has started to brown.
As you continue to whisk, slowly add in the warmed milk mixture. Cook, whisking, for another minute or two, until it is thickened and smooth.
Remove the skillet from the heat.
Start adding in the cheese, one handful at a time, whisking the cheese in until combined.
Add the salt, pepper and nutmeg and whisk until smooth.
When the pasta is finished cooking, drain and return it to the pot.
Pour the cheese sauce over the pasta and stir to combine. Pour into the prepared baking dish.
In a bowl, combine the Panko, Parmesan and parsley. Sprinkle over the top of the mac and cheese.
Bake in the preheated oven until the cheese is bubbly and the topping is browned, about 30-35 minutes.
Let the mac and cheese sit for about 10 minutes before serving.
