Picnic food: Spinach, sweet potato and goats cheese frittata

Because it's such beautiful summery weather, I decided to have a Sunday evening picnic in the park (leaving shortly). This is what we will be eating, along with grilled asparagus, beetroot, dill and yoghurt salad, and cucumber, lemon and mint salad. Frittata is great picnic food because you can just cut it into slices and eat it with your hands. The same isn't true of the salad (especially not the beetroot), so I will nonetheless be packing some picnic plates...
If anyone wants to join me, I will be dodging bullets in London Fields.
Ingredients
400g sweet potatoes150g of cooked, frozen spinach (make sure it's whole leaf spinach, not chopped frozen spinach)1 onion2 cloves of garlic10 eggs2 x 70g goats cheesesSalt and pepperOlive oil
Peel and dice the sweet potatoes and slice the onions. Take a large frying pan with a lid, and fry the onions and crushed garlic in olive oil for a minute or two. Then add the sweet potatoes and cover with the lid. Stir after a couple of minutes, and if necessary add a tablespoon of water to help steam the sweet potatoes. After about 10 minutes, test the sweet potatoes with a knife to see if they are done and then remove them from the heat and allow to cool.
Thaw the spinach and squeeze our any excess liquid. Beat the eggs in a large bowl and then add the spinach. Season well with salt and pepper. Next, take one of the goats cheese, cut into small cubes and then add to the egg mix. Finally, add the sweet potatoes and onion and stir until the ingredients are evenly mixed.
Wipe the pan with some kitchen towel and then place on a moderate to high heat with some more olive oil. Once the oil is hot, pour the frittata mixture into the pan and smooth to ensure that it is evenly distributed. Turn down the heat to low. Next, carefully slice the remaining goats cheese and arrange the slices around the top of the frittata. Place the lid on the pan and leave for around 20 minutes. When you remove the lid, the frittata should be mostly cooked, save for a small amount of liquid egg mixture in the centre. Finish the cooking process by placing the pan under a moderate grill for three or four minutes.
Allow the frittata to cool in the pan and then cut into 8-10 slices ready for your picnic