Photograph: Martin Poole
Preheat the grill to medium high. Cook the new potatoes in a pan of boiling salted water for 10-15 minutes until tender. Halve the broccoli spears and add to the pan with the other vegetables for the final 3 minutes of cooking time. Drain well, run under cold water, then slice the potatoes.
Meanwhile, heat the olive oil in a 22cm ovenproof nonstick frying pan and cook the onion gently for 8-10 minutes until softened.
Add the cooked potatoes and vegetables to the pan. In a jug, whisk together the eggs with some seasoning, the pesto and the chopped mint.
Pour the egg mixture over the vegetables in the pan, then use a fork to move the egg in from the sides towards the centre; cook for about 3 minutes until the egg begins to set. Top with the goats' cheese slices. Grill for 6-8 minutes, checking regularly, until the top of the frittata is set. Take off the heat and leave to stand for a few minutes.
Run a spatula around the edge to loosen the frittata. Slide on to a serving plate and scatter with the mint leaves.
Get ahead: make up to a day ahead and store in the fridge. Serve warm or cold.