Preheat the oven to 350 degrees. Grease a 9x13” baking pan and set aside.
Cook the noodles according to the package directions, to al dente, approximately 9 minutes.
In a small bowl or measuring cup, stir the chicken bouillon in the warm heavy cream; set aside to dissolve.
In a large bowl, add the noodles, tuna, sour cream, mayonnaise, garlic and onion powders, peas, pimento peppers, cheese, and green onions. Combine the ingredients well. Set aside.
In a shallow skillet or pan, heat the butter (or oil) over medium heat. Once melted, add the celery, onion, and bell pepper. Give a light pinch of salt and pepper. Sauté until just softened. (You can caramelize the vegetables if you’d like. Just account for a bit longer cooking time.) Add the garlic and stir for about 30 seconds.
Scrape the veggies into the bowl with the tuna mixture. Stir the milk-bouillon mixture once more and add to the bowl. Combine all the ingredients together and scrape into the 9x13” pan.
Sprinkle the potato sticks and parsley over the top of the casserole and bake for 25 to 30 minutes, or until the edges are bubbling and the top is nicely browned.
Serve very warm.