Preheat oven to 375 degrees Fahrenheit.

Add potatoes to a large pot and fill with water to reach about one inch above the potatoes. Generously salt the water. Bring to a boil over medium-high heat and cook until tender, about 15–20 minutes. Drain. While still hot, add margarine, nondairy milk, roasted garlic cloves and excess oil (if using), salt, pepper, and nutmeg. Coarsely mash, taking care not to over-mash, as that will make the potatoes gummy.

Meanwhile, heat the oil in a large skillet. Add the onions, garlic, carrots, celery, and bay leaf and cook until the onions are translucent.

Add the ground meat and saute until no longer pink, about four to six minutes. Stir in the tomato paste, oregano, salt, and pepper. Remove the bay leaf and discard.

Spread the meat mixture over the bottom of an oven-safe 9×13-inch baking dish. Gently spread the mashed potatoes on top, sprinkle with paprika, and spray with oil.

Bake for 30 minutes, until the top is golden.