Preheat your oven to 350 degrees.
Preheat a heavy skillet over medium-high heat, and then add the oil and onions. Sauté them until they are golden brown. Add the garlic and mushrooms and continue sautéing until all the liquid has evaporated and the mushrooms have lightly browned.
In a large bowl mix together the turkey, milk, breadcrumbs, egg, tomato paste, Worcestershire sauce, thyme and mushroom mixture. Season well with salt and pepper. Press the mixture into a loaf pan, or 8" by 8" baking dish and bake until lightly browned on top and firm, about 1 hour.
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