Preheat the oven to 200°C, fan 180°C, gas mark 6. Place the potatoes in a large pan and cover with cold water. Bring to the boil and cook for 10 minutes, until tender. Drain the potatoes, let cool slightly then slice into thin rounds.
Heat the olive oil in a 25cm non-stick, ovenproof frying pan and cook the sliced onion for 5 minutes, until soft.
Add the potato slices, beaten eggs, crumbled feta, peas and mint to the pan and stir to combine. Leave over a medium heat for 5 minutes, until the bottom of the frittata has set.
Transfer the pan to the oven and cook for 20-25 minutes, until the frittata has fully set. Cut into wedges and serve with the halved baby plum tomatoes.
* Please note, this recipe is not suitable for vegetarians as it contains feta.