Toast the coriander seeds in a dry frying pan over a low–medium heat until fragrant and aromatic.

Remove to a mortar and pestle, then add the salt and lightly crush.

Lightly chop the thyme leaves with a knife, not too finely. Mix together and set aside.

Heat the oven to 220°C (430°F).

Place two heavy duty baking trays on the middle shelf of the oven and heat for at least 30 minutes.

Cut two sheets of baking paper, around 30 × 30 cm (12 × 12 in), and place on a benchtop.

Place one sheet of puff pastry on each sheet of baking paper. ‘Dock’ the puff pastry by pricking it all over with a fork. Divide and spread the mascarpone evenly over both pastry bases in a thin layer. — Scatter the grated cheese on top, then season with sea salt and pepper.

Trim the ends from each potato and, using a mandoline, finely slice the potatoes into a bowl. Do not wash or rinse the potatoes.

Starting from one side, arrange the potatoes in lines on top of the cheese so that they overlap by about half a slice, making sure you take them right up to the edge of the pastry.

Slide the baking paper with the pastry onto cold trays and refrigerate for around 30 minutes to chill.

When chilled, drizzle with olive oil and season well with the coriander and thyme salt.

Slide the baking paper and pastry onto the preheated trays in the oven and bake for about 15 minutes.

Remove the paper from beneath the tarts and rotate 180 degrees, then bake for a further 5–10 minutes, until crisp and golden.

Remove the tarts from the oven and cool on wire racks.

To serve, flash the tarts in the oven for 2 minutes at 200°C (390°F), placed directly on the oven racks. Cut into triangles or squares and serve.