Ingredients out • Kettle boiled • Oven grill on high • Food processor (fine slicer) • Medium lidded pan, high heat • Large high-sided roasting tray, high heat • Large frying pan, medium-high heat

START COOKING

1. Scrub the potatoes clean, finely slice in the processor, then tip into the medium pan and cover with boiling water and the lid.
2. Peel the onions, finely slice in the processor, then tip into the roasting tray with 2 tablespoons of oil, crumble in the stock cube and season with sea salt and black pepper.
3. Tear in the sage leaves and stir regularly, adding a splash of water if they start to catch.
4. On a large sheet of greaseproof paper, toss the chicken with salt, pepper and the rosemary leaves, then fold the paper over and bash and flatten the chicken to 1.5cm thick with a rolling pin.
5. Put into the frying pan with 1 tablespoon of oil, turning after 3 or 4 minutes, until golden and cooked through.
6. Drain the potatoes well in a colander, then tip into the onion pan, stir together and arrange in a flat layer. Pour over the cream, then finely grate over the Parmesan and pop under the grill on the top shelf.
7. Halve the leeks lengthways, rinse under the tap, then finely slice. Put into the empty lidded pan on a high heat with 1 tablespoon of oil, stirring often.
8. Finely slice the bacon and add to the chicken pan, tossing regularly.
9. Stir the spinach and peas into the leeks and once the spinach has wilted and the peas are tender, pile on a board or platter with the chicken and bacon on top. Serve with the gratin.