Spray a 9x13-inch pan with nonstick cooking spray and preheat oven to 350°F.
Cook pasta according to package directions, but cook it the least amount of time (i.e. if the package says cook 10-12 minutes, cook it for only 10 minutes, or until it’s slightly al dente). Drain and set aside.
Meanwhile, in a large saucepan or pot, melt 4 tablespoons Challenge Butter over medium heat. Whisk in the flour and cook for about a minute, then whisk in stock and milk until no lumps remain. Whisk in spices.
Switch to a wooden spoon or spatula and stir almost continuously until the mixture thickens. This will take a few minutes, and will happen just as the mixture starts to simmer. Add in the cheese and stir until it’s melted through then remove the mixture from the heat.
Stir in the chicken, peas and pasta. Pour into prepared pan.
Make the topping: melt 4 tablespoons Challenge Butter. Pour over crushed crackers in a small bowl and stir with a fork to moisten all the crumbs. Sprinkle evenly over casserole.
Bake 20-30 minutes or until the mixture is bubbly around the edges and the crackers have browned a bit.
Serve hot. Store leftovers in an airtight container for up to 3 days.