Preheat your oven to 180°C (350°F).

Cook the rice according to package instructions and set aside.

In a large skillet, heat a bit of olive oil over medium heat. Add the chopped onion and cook until translucent.

Add the sliced mushrooms and diced eggplant to the skillet. Cook until the vegetables are tender, about 5-7 minutes.

In a large bowl, beat the eggs and mix in the yogurt or sour cream until well combined. Season with salt.

Add the cooked rice and sautéed vegetables to the bowl and mix well.

Transfer the mixture to a greased baking dish. Sprinkle the chopped pistachios on top.

Bake in the preheated oven for 35 minutes, or until the top is golden and the casserole is set.

Let the casserole cool for a few minutes before serving.