Heat olive oil in a medium saucepan over medium heat, saute onions until tender 5-10 minutes. Add the garlic and saute another minute or two. Add the butter to the pan, once melted whisk in the flour, and cook for 1 minute. Whisk in the turkey stock, milk, nutmeg, pepper, and salt. Cook and whisk until it comes to a boil and starts to thicken. Stir in 1 1/4 cups of Parmesan cheese and remove from the heat.
1 tablespoon olive oil, 1/2 medium onion, 1-2 garlic cloves, 1/4 cup butter, 1/4 cup all-purpose flour, 1 1/2 cups turkey stock, 1 cup whole milk, 1/2 teaspoon salt, 1/2 teaspoon fresh ground pepper, 1/4 teaspoon fresh grated nutmeg, 1 3/4 cups Parmesan cheese