Peel the potatoes, chop into even-sized chunks and cook in a large pan of boiling salted water for 15 minutes, or until tender.

Meanwhile, halve the tomatoes, squeeze out the seeds and dice the flesh.

Toss with a good pinch of sea salt and sit the tomatoes in a sieve to drain.

Trim and finely slice the spring onions.

Coarsely grate the cheeses.

Squeeze out any excess water from the tomatoes and mix with the spring onions and cheese.

Lay out a 40cm x 30cm sheet of greaseproof paper.

Preheat the oven to 200°C.

Drain the potatoes, then mash really well with 2 tablespoons of extra virgin olive oil and season to perfection.

Tip the mash on to the sheet of greaseproof.

Once cool enough to handle, flatten out with oiled hands to a rectangle about 1cm thick.

Spread the tomato mixture over one half, leaving a 2cm gap around the edge, then in one swift move use the paper to help you flip the other half of the mash on top.

Unpeel the top half of greaseproof, then use the paper to help you slide the whole thing into a 20cm x 30cm baking tray.

Rip off the overhanging half of the paper, then fold and press in the edges of the mash and patch up any gaps, using a knife to help you smooth it out and make a pattern, if you like.

Brush with 1 tablespoon of olive oil and bake for 50 minutes, or until golden and crisp.

Slice and serve with lemon-dressed rocket.