Pre-heat the oven to 350º. Pre-cook the pie crust for 10 minutes (use store bought for a quicker recipe).
In a large pan (warm some oil first if desired), start by cooking the onion and green onion on medium-high heat with a pinch of salt for about 5-7 minutes. Stir often. When the veggies are browned, then add the garlic and cook for one more minute, but not longer so it does not burn.
Add the spinach, stir and cook until wilted, about 3-5 minutes. Remove from the heat and set aside to let it cool down.
In a blender, combine the tofu, cornstarch, nutritional yeast and salt.
Remove the blender from its base and add the spinach-onion mixture to it. Stir to combine using a long spoon (do not blend!). Then, transfer the creamy spinach mixture over the pre-baked crust. Make sure the spinach is well distributed.
Bake in the oven for 30 minutes. Then, let the quiche set at least for 20 minutes at room temperature before slicing and eating.