mashed potatoes with cheese

*sigh* Comfort food.  Enough said. Shepherd's Pie 3 pounds baking potatoes, peeled & sliced into 1" rounds 1 tbsp vegetable oil 6 medium carrots, chopped 6 celery stalks, chopped 1 large onion 1/2 tsp dried thyme 1/4 cup all-purpose flour 1/4 cup tomato paste 1 pound ground beef 1 pound ground pork 1 cup whole milk 1 1/2 cups shredded aged cheddar cheese Preheat oven to 450F. Place potatoes in a large saucepan, and cover by an inch of salted water. Bring to a boil; …