Preheat oven to 350°. Brush both sides of tortillas with oil; cut into 1⁄2-inch strips. Spread evenly on a baking sheet; sprinkle with salt.
Bake, stirring occasionally, until lightly browned and crisp, approximately 10 minutes. Let cool completely.
In a large skillet, cook sausage and onion over medium heat, stirring occasionally, until browned, approximately 8 minutes. Drain; set aside.
In same pan, melt butter over medium heat. Add flour; cook, whisking constantly, 1 minute. Whisk in milk, salt, and pepper. Bring to a boil over medium-high heat, whisking constantly. Reduce heat to medium-low. Cook, whisking constantly, until thickened, 2 minutes. Remove from heat.
Stir in 1⁄2 cup cheese until melted. Stir in sausage mixture and cooked pasta. Sprinkle with remaining 1⁄2 cup cheese and cilantro. Serve with tortilla strips.
Recipe by Taste of the South at https://tasteofthesouthmagazine.com/chorizo-macaroni-cheese/