Cook the macaroni: Heat several quarts of water in a large stockpot over high heat, and cook noodles according to package directions until just barely al dente, the minimum cook time on the package. Drain and set aside in a strainer, adding a few drops of oil or cold water and stirring to ensure they don’t stick together. Preheat the oven to 425F.

Cook the chicken & veggies: In a large skillet or Dutch Oven (use it for baking the mac and cheese too!), heat oil over medium heat. When hot, add the onion, celery and carrot, and a small dash of salt. Cook for about 8 minutes, stirring occasionally, until the carrots are soft. Add the chicken and a large dash of salt. Continue to cook for another 7-8 minutes, stirring occasionally, until the chicken is cooked through. Remove the chicken and veggies from the pan and set aside.

Make the sauce: Reduce heat to medium low. Return the same pan to heat and melt the butter. Add flour to the pan and whisk continuously until the butter and flour have thickened (around 90 seconds). Add the milk, 1/4 cup at a time, whisking continuously until completely added. Let the milk heat for about 2 minutes, while you continue to whisk. Add cheese (reserve 1/2 cup for topping), and whisk continuously as it melts. Add greek yogurt, buffalo sauce, Ranch seasoning, garlic powder and pepper, and continue to whisk until a smooth sauce has formed (about 1 minute). Remove from heat.

Put it together: Add the cooked macaroni, and the cooked chicken veggie mixture to the pot with the sauce. Stir until well-mixed. Pour everything into a 9×13 inch casserole pan. Top with remaining cheese and optional crushed crackers. Bake in the preheated 425F oven for 13-15 minutes until the cheese is bubbly and top is golden to your liking. Enjoy immediately or refrigerate and enjoy as leftover for up to 4 days.