Salt and freshly ground black pepper (use sparingly, as the stock is salted)
(2 tbsp chopped fresh parsley, optional)
Method
Preheat the oven to 190°C. Grease a 9×9-inch baking dish.
Heat 2 tablespoons of olive oil in a large skillet over medium heat. Sauté the onions until soft (about 5–7 minutes). Add the mushrooms and cook until most of the liquid evaporates (about 5–7 minutes). Stir in 1 teaspoon of the mushroom soup stock mix powder; adjust salt and pepper if needed.
In a large bowl, whisk the eggs with the potato starch and optional herbs. Fold in the warm mushroom–onion mixture.
Pour the batter into your prepared dish, drizzle with the remaining olive oil, and bake for 45–55 minutes until the top is golden and the kugel is set.