Bring a large pot of water to a boil, salt the water and cook the pasta until 1 minute shy of al dente. Drain well.
Meanwhile, in a skillet, heat the oil, one turn of the pan, over medium-high. Add the chorizo and cook, stirring occasionally, until the fat renders and the meat is light brown, about 2 minutes; drain on a paper towel-lined plate.
Arrange a rack in the center of the oven; preheat the broiler.
In a large saucepot, melt the butter with garlic over medium to medium-high heat and stir until fragrant, about 30 seconds. Whisk in the flour. When it bubbles, whisk in the milk; season with salt, cayenne, smoked paprika and dry mustard. Whisk until thick enough to coat the back of a spoon, about 3 minutes.
In a large bowl, mix the cheeses. Add 3 cups of the cheese mixture into the sauce, 1 cup a time, stirring until melted and smooth between additions. Remove from heat and stir in the piquillo peppers.
Mix the pasta and chorizo into the cheese sauce and pour into a 1 1/2- to 2-quart baking dish. Top with the remaining cheese mixture; broil until browned and bubbly, 3-5 minutes. Top with the scallions and parsley. For an entrée, serve with salad.
From Rachael Ray Every Day, November 2017