1. Preheat the oven to 170°C (approximately 340°F).
2. Slice the onion and sauté it in a wok with a drizzle of olive oil until golden.
3. It should not brown.
4. Cut the zucchini into rounds and the eggplant into half-rounds.
5. Remove the onions from the heat and set them aside.
6. It's now time for the zucchini and eggplant to cook with a drizzle of olive oil, adding salt.
7. When the vegetables are halfway cooked, add the onions and cook for another 5 minutes.
8. Beat the whole eggs in a bowl with a whisk, then add the heavy cream.
9. Place half of the vegetables, then the goat cheese, and the remaining vegetables in a gratin dish, pouring the egg-cream mixture over it.
10. The dish is ready to go into the oven!
11. If your oven is too hot and the vegetables on top are browning faster than the dish is cooking, cover the dish with aluminum foil to allow everything to cook without the top burning from the excessive heat of the oven.