1. Preheat oven to 350 degrees Fahrenheit. Spray a 9×13-inch pan very well with nonstick cooking spray. (You can also make these in muffin tins or in round pans and cut into triangles.)
2. Preheat a large frying pan on medium-high heat. Add oil and onions and sauté for three to four minutes, until onions are translucent. Add garlic and sauté another two to three minutes. Add mushrooms and sauté for 15 to 20 minutes, until all liquid that is released has evaporated. Remove from pan and allow to cool completely.
3. While mushrooms cool, prepare sautéed liver and onions: Place onion into the frying pan on medium-high heat and sauté for three to four minutes, until they begin to brown. Add garlic and sauté another two minutes.
4. In a small bowl, mix potato starch with one teaspoon salt. Coat liver with potato starch mixture.
5. Add liver to the frying pan and sauté for two to three minutes, until the potato starch is browned. Lower flame and cook covered for 20 to 30 minutes, until onions are soft and caramelized.
6. Add water or chicken stock, one teaspoon salt, and pepper and bring to boil. Lower flame and simmer for 20 minutes, until sauce thickens a bit.
7. In a large mixing bowl, place mushroom mixture. Add remaining kugel ingredients. Pour into prepared pan and bake for 35 to 45 minutes, until top is golden brown. Cool completely before removing from pan.
8. Reheat and serve with hot liver on top.