1. Preheat the oven to 400 degrees Fahrenheit.
2. Heat olive oil in a sauté pan over medium heat. Add onions and sauté until soft, five to seven minutes.
3. Season potatoes with salt and pepper, and add half the onions (leave the rest of the onions in the pan).
4. Spray a baking dish well with nonstick cooking spray and press the potatoes along the bottom and sides of the dish, spreading evenly. Spray again with nonstick cooking spray. Cover and bake for 20 minutes. Uncover, lower oven temperature to 375 degrees Fahrenheit, and bake an additional 25 minutes, until crisp.
5. Meanwhile, prepare the filling. Heat the sauté pan (with the remaining onions) and add zucchini, squash, pepper, tomato, and mushrooms. Sauté until soft. Season with salt and pepper. Remove from heat and let cool; add eggs and mix well. Pour filling into crust.
6. Lower oven temperature to 350 degrees Fahrenheit and bake for 45-50 minutes, until quiche begins to turn golden.
To make these in mini size, don’t cook and mash the potatoes. Instead, simply grate three potatoes (instead of four) in the food processor (as you would for latkes) and mix with two eggs (instead of three). Season with salt and pepper, and press mixture along the bottom and sides of a muffin pan. Follow the rest of the recipe; final cooking time will be 30-35 minutes (instead of 45-50).
This was a pretty time-consuming dish to make, but it is very tasty! I added ~4 cloves of garlic and some extra herbs and seasoning throughout the cooking process, and it still could have maybe used a bit more, but I really loved the textures and flavors of this dish, plus it’s relatively healthy!