Method

1. Preheat the oven to 350°F / 180°C.
2. Fill the bottom of a steamer with about 1 inch / 2.5 cm of water. Cover and bring the water to a simmer over medium heat.
3. Add the potato pieces to the steamer basket and steam for 12 minutes, or until a skewer meets just a bit of resistance when inserted into the centre of a piece of potato. Remove the potatoes from the saucepan and cool completely.
4. Heat the oil in a 12 inch / 30 cm non-stick ovenproof frying pan over medium-high heat. Add the potatoes, sprinkle with salt and pepper, and sauté for 2 minutes, or until the potatoes are tender and pale golden.
5. Add the mushrooms, bell pepper, and eschalots and cook for 4 minutes, or until the vegetables soften slightly. Stir in the zucchini and reduce the heat to medium-low.
6. Whisk the eggs, salt, and pepper in a large bowl to blend well.
7. Pour the egg mixture over the vegetables in the pan.
8. Add the tomatoes and feta cheese, and cook without stirring for about 5 minutes, or until the egg mixture is almost set but the top is still loose. Transfer the pan to the oven and bake for 20 minutes, or until the centre is just set.
9. Using a silicone spatula, loosen the frittata from the pan, then slide the frittata onto a plate and serve.