In a large sauté pan set over medium heat, melt butter. Add the onion and garlic and cook for a few minutes, until softened and fragrant. Add the flour and cook for about 2-3 minutes, stirring occasionally. Whisk in hot milk and stir until sauce thickens, about 7-8 minutes.
Stir in 2 cups of the cheese and the parsley, cilantro, tomato paste, chili powder, oregano and chili peppers. Spread 1/2 (one-half) cup sauce in a 8” square casserole dish. Top with the rice, and then the chicken. Cover with the remaining sauce and let cool (and refrigerate if you don’t want to bake it right away).
Bake in a 400° F oven for 30 minutes, then reduce heat to 375°F. Sprinkle on the chips and remaining cheese, and bake for an additional 10-15 minutes.