Peel and thinly slice sweet potatoes (preferably with a mandoline). Cut off the end of a handful of slices to get a flat edge. Add slices to a bowl, drizzle with avocado oil and work oil into the slices with your hands.
Line a 9" pie dish with the sweet potato slices. The round slices for the bottom and the slices with the flat edge for the sides. Ensure they all overlap. Then prebake for 15 minutes. Set a timer!
In the meantime, finely chop shallots and galric and then brown them in a large pan over medium low heat in a little avocado oil. Once brown, add spinach and sauté for about 30 seconds or until wilted. Remove from the heat and let cool completely.
Add eggs, half of the grated Parmesan, milk, and sea salt and pepper to taste to a large bowl and whisk until well combined. Then add cooled spinach mixture and use a spatula to mix in. Do NOT add hot spinach, it has to be cold enough to not start cooking the eggs.
In a separate bowl mix ricotta, cheddar cheese and remaining grated Parmesan.
Carefully pour egg filling into prebaked sweet potato crust and then add dollops of the ricotta mixture in an uneven pattern all over.
Bake the quiche for 40-45 minutes or until the eggs are set.
Turn on the broiler the last minute or two for a nice brown top. Garnish with basil if desired.