Pre Heat the oven to 190C/170fan Gas 5.
Heat the oil in a 10" oven proof pan and saute the uncooked tomatoes and sliced potatoes for 1 minute. Add the remainder of the cooked vegetables and allow to heat through.
Meanwhile, whisk the eggs and creme fraiche together in a large bowl. seaon with salt and freshly ground black pepper.
Make sure the sides of the pan are coated with the oil and add the egg mixture to the pan. Cook for approximately 5 minutes and then add the mozzarella, olives, and scatter over the calendula petals and nasturtium leaves.
Transfer to the oven and bake for approximately 30-35 minutes until the frittata is firm to touch and slightly puffed up.
To serve - Top with nasturtium flowers and chopped nasturtium leaves and serve with a salad of salad and nasturtium leaves.