Creating Tuna Mushroom Casserole is straightforward if you follow these simple steps:

1. Preheat Oven: Preheat your oven to 350°F (175°C).
2. Cook Noodles: Prepare egg noodles according to package instructions; drain and set aside.
3. Sauté Vegetables: In a skillet, heat olive oil over medium heat. Add chopped onion and minced garlic, sautéing until soft and translucent.
4. Combine Ingredients: In a large bowl, mix together the drained tuna, cream of mushroom soup, milk, cooked noodles, peas, sautéed onions, black pepper, salt, and thyme until well combined.
5. Add Cheese: Gently fold in half of the shredded cheddar cheese into the mixture.
6. Transfer to Baking Dish: Pour the tuna mixture into a greased 9×13-inch baking dish, spreading it evenly.
7. Top with Breadcrumbs: Sprinkle breadcrumbs over the top of the casserole, followed by the remaining cheddar cheese.
8. Bake: Place the dish in the preheated oven and bake for 30-35 minutes or until the casserole is bubbly and the top is golden brown.
9. Cool and Serve: Remove the casserole from the oven and let it cool for 5-10 minutes before serving.

These steps will guide you in creating this incredible casserole effortlessly.