Start by spiralizing the zucchini and place the strands in a colander; add a teaspoon of salt and mix well. Set your colander in the sink or over a large bowl (make sure it’s elevated so the zucchini doesn’t come in contact with the water that it will release) and place a sturdy plate that fits snuggly over the zucchini. Add a weight over that plate and let that rig sit for about 30 minutes, until the zucchini has released all of its water.
With the help of a mandolin, slice the sweet potato as thinly as possible and reserve.
Preheat your oven to 375°F
Melt some cooking fat in a heavy skillet (cast iron preferred) set over medium-high heat. Add the onions and celery, sprinkle lightly with salt and cook until softened and fragrant, about 2-3 minutes. Add the mushrooms, sprinkle with a little bit more salt and continue cooking until they get all soft and golden brown, about 5 minutes.
Remove the vegetables to a plate, put the skillet back over the heat source, crank up the heat to high and add the ground beef. Break the meat into little pieces, sprinkle with yet a little bit more salt and cook until the beef turns dark brown and starts to become crispy, about 10-12 minutes.
When the beef is cooked to your liking, add the salted herbs (omit if you don’t have but make sure you adjust saltiness), Dijon mustard, oregano, paprika, pepper, cayenne and water. Stir until well combined and continue cooking for a few minutes until the liquid has completely evaporated. Add the vegetables back into the pan and stir well.
Transfer the meat to a baking dish and then arrange the spiralized zucchini over the meat, followed by sweet potato slices. Pour the melted ghee over the potatoes, cover with aluminum foil and bake in a 375°F oven for 55-60 minutes, until the potatoes are soft.
Remove the foil and broil for 3-5 minutes to crisp up the potatoes a little bit and give them a beautiful golden color.
Remove from the oven, let rest for 5-10 minutes before serving.