- Preheat the oven to Gas Mark 6, 200°C (400°F).
- Wash the potatoes and cut them into 3mm thick slices using a mandolin or sharp knife.
- Arrange the potatoes, overlapping, in four circles on greased baking paper.
- Brush with beaten egg and season with salt and pepper. Cover the potato slices with baking paper and a baking tray so that the potato slices do not curl up. Bake covered for 15 to 20 minutes.
- In the meantime, mix the ricotta with finely chopped oregano and lemon zest. Season with salt and pepper.
- Remove potato bases from the oven and cover each one with ricotta and top with pancetta. Sprinkle with the oregano and basil and bake for 10 minutes in the middle of the oven.
- Just before serving, cut into equal portions and sprinkle the rocket on top.
Note: Use a combination of floury and sweet (orange/purple) potatoes for a more colourful palette.