• Preheat the oven to 375°. Butter a 9 x 13 inch baking dish and set aside.
• Cook the egg noodles in salted boiling water according to package directions. Drain and immediately place the noodles in a large bowl filled with ice water to stop cooking. Once cooled, drain and then pour the pasta into a large bowl with the tuna, peas and cheese. Toss to combine.
• Set a large pan over medium heat. Add the 2 tbsp of butter, the olive oil, onions, and thyme. Season with salt and pepper and continue to cook until the onions are tender, about 5 minutes.
• Add the mushrooms, season with salt and cook until tender and darkened, about 5 minutes. Add the Worcestershire sauce. Sprinkle the flour over the entire pan. Stir until the flour is completely absorbed.
• Raise the heat to medium-high and add the chicken stock. Cook until slightly thickened, about 5 minutes.
• Slowly stir in the heavy cream. Simmer until the cream is thickened slightly, about 5 minutes. Salt and pepper to taste. Pour the mushroom sauce over the prepared noodles in the large bowl and stir to combine. Pour entire mixture into the prepared baking dish.

For the Topping

• In a small bowl, combine the breadcrumbs and olive oil. Season with a sprinkle of salt and pepper. Stir until the crumbs have absorbed the oil evenly. Sprinkle the breadcrumb mixture evenly over the casserole dish and place, uncovered, into the oven. Bake until the sides are bubbly and the top is golden brown, about 35 minutes.
• Remove from the oven and let rest for 5 minutes before serving.