Peel and cut the potatoes. Cover them with water in a medium saucepan and heat to boiling on high heat. Turn down the heat to medium and cook until they are soft but not soggy. This will take about 15 to 20 minutes.
While the potatoes are cooking, gather the ingredients for your meat layer.
In a medium pan over medium heat, add 1 teaspoons oil. When hot, add the ground meat (or extra-firm tofu crumbles). Sprinkle with the turmeric and mash the meat into crumbles and stir occasionally for about 7 to 9 minutes or until completely browned. Remove the meat with a slotted spoon and discard any remaining fat.
Using the same pan, heat the remaining 2 teaspoons of oil over medium-high heat and add onion and salt. Cook until the onions are golden, about 8 minutes. Reduce heat if necessary to keep the onions from sticking, and/or add a tablespoon of water.
If you haven't already, check on the potatoes for doneness, drain and set aside.
Add the ginger garlic paste to the onions, stir for 1 to 2 minutes until it no longer smells raw. Stir in the chili powder, cloves, cinnamon, and coriander. Stir, cooking the spices for another minute, then add the tomato sauce. Cover and simmer for 6 minutes until the sauce thickens slightly and turns a darker color.
Return the meat (or tofu) to the pan with the onions and tomato mixture. Cook for 7 more minutes, stirring several times, continuing to break down the meat.
The final sauce should be moist and saucy. If you need more liquid, add some stock or more tomato sauce. Taste for salt and chili pepper, adjust as needed.
Preheat the oven to 400°F (200°C).
Mash the potatoes, then add the butter, dairy, salt, pepper, and cheese (if using). Add a bit more liquid if the mixture is too stiff. It needs to be spreadable, but not soupy.
Layer the meat and tomato mixture into the baking pan.
Dollop big spoonfuls of the mashed potatoes onto the top of the meat and spread out evenly beginning with the edges. This seals in the juices from bubbling up over the potatoes. Decorate the smoothed top as the spirit moves you, using a fork. Then garnish with melted butter and grated parmesan, if using.
Bake for 25 minutes or until hot, bubbly, and the potatoes are golden brown. Using a metal utensil—a spoon or fork handle—test the center of the pie. It is ready when the utensil returns hot.
Remove from the oven and allow the shepherd's pie to rest on a cooling rack for 10 minutes before serving.
If you are looking for lower glycemic vegetables to swap for the mashed potatoe layer, consider mashed butternut squash or cauliflower
Add sweet potato cubes, celeriac, fennel, turnips, or small pieces of cauliflower to the meat mixture to up the vegetable quotient. Make sure the vegetables are almost cooked through.
Shortcut: Use frozen vegetables
Instead of mozzarella cheese for the mashed potatoes, you might use goat cheese, feta, or cheddar cheese. Since all of these cheese are more flavorful, you might start with 1/2 a cup, taste, then add more if needed.