Place the tofu, nutritional yeast, soy sauce or tamari, lemon juice, and turmeric into the bowl of a food processor fitted with an S-blade.
Blend everything until smooth, stopping to scrape down the sides of the bowl as needed. You can add splash or two of milk if needed to get the mixture smooth, but keep it to a minimum.
Coat the bottom of a large skillet with olive oil and place it over medium heat.
When the oil is hot, add the potato. Sprinkle with a bit of salt and pepper, and cook it for about 10 minutes, flipping occasionally with a spatula, until it just begins to soften.
Add the leeks and cook everything about 5 minutes more, until the leeks are soft, and the potatoes are fork tender and crispy on the outsides.
Add the garlic and cook just until very fragrant, about 1 minute more.
Preheat the oven to 375°.
Transfer the tofu mixture and the potato leek mixture to a large bowl and mix until the potatoes and leeks are evenly distributed. (Alternatively, you can save a dish by letting the skillet cool a bit and then mixing everything in there.)
Transfer the mixture to the pie crust and smooth out the top with a spatula.
Place the filled crust into the preheated oven and bake until the center is set, and the crust is browned around the edges, about 30 to 35 minutes.
Allow the quiche to sit for a few minutes before cutting. Serve with a sprinkle of kala namak, if desired.