Feta Spinach and Basil Omelette Muffins

Name: Feta, Spinach, and Basil Omelette Muffins
Ingredients: Cooking spray or sunflower oil, for greasing; 8 free-range eggs; 8 sun-dried tomatoes, drained well and roughly chopped; Large handful of baby spinach, roughly chopped (about 2 Tablespoons); Good pinch of freshly grated nutmeg; 1/2 cup feta cheese, roughly broken into bite-sized pieces; A few fresh basil leaves; Sea salt and freshly ground black pepper; 1/2 cup arugula, watercress, or mixed salad leaves; 3 tablespoons extra-virgin olive oil; 1 tablespoon balsamic vinegar