Preheat your oven to 350°F and butter a 9x13-inch baking dish generously. Bring a large pot of salted water to boil, then cook the egg noodles according to package directions until just al dente (about 8-10 minutes). Drain and set aside—don't rinse them.

While noodles cook, heat two tablespoons butter in a large skillet over medium-high heat. Brown the ground beef, breaking it into small pieces, for about 5-7 minutes until fully cooked through. Drain excess fat if needed, leaving about one tablespoon in the pan.

Add the diced onion and sliced mushrooms to the beef, cooking for 3-4 minutes until softened and fragrant. Stir in minced garlic and cook another minute. The kitchen will smell incredible at this point.

Reduce heat to medium and pour in the beef broth, cream of mushroom soup, and Worcestershire sauce. Stir well to combine everything smoothly. Add the sour cream and dried thyme, stirring gently until this beef noodle casserole base is fully incorporated and creamy. Don't boil—just warm through for 2 minutes.

Combine the cooked noodles, beef mixture, and frozen peas in your prepared baking dish. Stir in one-and-a-half cups of the shredded cheddar cheese, reserving the remaining half cup for topping. Season with salt and pepper to taste.

Mix the remaining cheddar cheese with panko breadcrumbs and sprinkle evenly over the casserole. Bake for 25-30 minutes until the top is golden brown and the filling is bubbling at the edges.

Remove from the oven and let rest for 5 minutes before serving so it holds together beautifully. This resting time makes serving cleaner and prevents the filling from running all over the plate.