Preheat the oven to 400 degrees F.
Lightly grease a 9 x 13 baking dish with olive oil.
Dice approximately 3 cups of leftover cooked turkey, place in a bowl, and set aside.
In a large skillet over medium heat, add 1 tablespoon of butter and 1 tablespoon of olive oil eachAdd the mushrooms and sauté over medium-high heat until the liquid from the mushrooms evaporates and the mushrooms begin to brown. Remove from heat and set aside. In the same skillet, add another tablespoon of olive oil and the onion, garlic, and thyme. Sauté until the onion is translucent and soft, about 8 minutes. Adjust the heat as needed, making sure not to overcook or brown the onions.
Once the onions are translucent and soft, add the mushrooms back to the pan and add the cooking sherry or white wine. Simmer until it evaporates, about 2 minutes. Transfer the mushroom mixture to the bowl and set aside.
Melt 3 more tablespoons butter in the same pan over medium-low heat. Add the flour and whisk for 2 minutes. Flour butter mixture will slightly bubble on edges.
Whisk in the milk, cream, broth, nutmeg, 1 teaspoon of Kosher salt, and ½ teaspoon black pepper.
Increase the heat to medium-high and simmer until the sauce thickens slightly, whisking often. The sauce will thicken in 5-8 minutes. Remove skillet from heat and set aside.
While the sauce is simmering and thickening, bring a large pot of salted water to a boil. Add the egg noodles and cook until al dente (tender but firm to the bite). Drain and return to the pot.
In the pot with the cooked egg noodles, add the diced turkey, mushroom mixture, and peas. Pour the sauce over the noodles and fold to combine and coat the mixture with the sauce.
Transfer the pasta mixture to the prepared baking dish.
In a small bowl, combine the breadcrumbs and cheese and stir to blend. Sprinkle the cheese mixture over the pasta.
Bake, uncovered, until golden brown on top and the sauce bubbles, about 25 – 30 minutes.