Preheat the oven to 350º F.
Add the potatoes to a large pot and add enough water to cover the potatoes. Add a pinch of sea salt and bring to a boil. The potatoes are done when easily pierced with a knife, about 15-20 minutes.
While the potatoes are cooking, add 1 tbsp. of the cooking fat to a large skillet and heat over medium-high heat. Once the fat is hot, add the ground meat. Sprinkle with a small pinch of sea salt and the Italian spice blend. Use a spatula to stir and break up meat while browning.
In a medium skillet, add the remaining 1 tbsp. of cooking fat to the pan and heat over medium-high heat. Add the onions and garlic and sauté until translucent. Turn the heat down to medium and add the spinach and cook until wilted. Remove from heat.
When the meat is cooked through, add the jar of tomato sauce and mix to combine.
When the potatoes are done, drain and mash with a potato masher. Add a pinch of sea salt and a tbsp. of butter.
In a large casserole pan, layer the mashed potatoes, the spinach/onion/garlic mix, and then meat sauce mixture. Put in the oven and cook for 15 minutes.
Before serving, garnish with basil and parmesan cheese and serve.