1. Pre-heat the oven to 180°C / fan 160°C / gas 4.
2. Heat oil in an oven proof frying pan on the hob, add the onion and sweet potato slices and sweat over low heat with the lid on until the potatoes are almost cooked through.
3. Add the baby spinach, then season with nutmeg, some pepper and a pinch of salt.
4. Beat the eggs in a bowl with the Alpro Cuisine and feta. Season with freshly ground pepper. Pour the eggs over the vegetables and place the pan in the oven for 15-20 minutes. Let it bake slowly, until the frittata is airy and the top is almost set.
5. Mix the balsamic vinegar and olive oil in a small bowl. Add the halved tomatoes and chopped chives and leave to marinate.
6. Serve the frittata with a simple green salad of spinach leaves and marinated cherry tomatoes. Fresh!