Wash the potatoes and cut them so they're in similarly-sized pieces suitable for skewers.
Boil the potatoes in salted water until just cooked through. Drain and rinse the potatoes, then thread onto skewers.
In a small bowl, mix the oil and mint together. Brush the mint oil onto the skewered potatoes and barbecue until lightly charred. Alternatively, cook them indoors on a griddle pan. Allow to cool slightly.
Meanwhile, boil the sweetcorn cobs for a few minutes until tender. Grill on the barbecue or in a griddle pan until lightly charred. Allow to cool, then slice the corn kernels from the cob.
Boil the peas for a few minutes until cooked. Drain and set aside.
Spiralize or julienne the carrot and apple and add to a large bowl with the grilled potatoes, corn kernels, peas and shallots. Add the mayonnaise and gently toss to coat. Drizzle with the lemon juice and serve cold.