Preheat your oven to 350 degrees Fahrenheit and spray a 9×13 baking dish with nonstick spray.
In a 4-quart Dutch oven, heat the olive oil over medium-high heat. Add the chopped celery, red bell pepper, and onion. Cook these until the onion becomes translucent and the celery and bell pepper are tender, about 5-6 minutes.
Add the minced garlic and sauté for an additional 30 seconds, being careful not to let it burn.
Reduce the heat to medium and stir in the cream of chicken soup and half and half. Mix well to combine.
Once it has heated through, add the shredded cheese, stirring until melted and creamy.
Add the cooked egg noodles and shredded chicken to the cheese sauce, stirring gently to combine all the ingredients.
Season with parsley, salt, and pepper to taste.
Remove from heat and transfer the mixture to the prepared baking dish.
In a ziplock bag, crush the Ritz crackers with a rolling pin until they are coarse crumbs. Pour these into a medium bowl.
Stir the melted butter and one cup of shredded cheddar into the crushed crackers until they are well combined.
Spread the cracker mixture evenly over the casserole.
Pop the dish in the preheated oven and bake, uncovered, for 15 minutes or until the cheese is melted and bubbly.
Serve hot and enjoy this comforting dish!