Lamb en croûte with redcurrant sauce

Season the lamb well. Heat the oil in a frying pan and fry three fillets over a high heat for 5 minutes until seared on the outside. Remove from the pan and repeat with the other 3 fillets. Set aside until cold.

Unravel the whole pack of pastry on a floured surface and cut into four rectangles. Cut the half pack to make two rectangles. Roll out each piece to make the rectangles 2.5cm larger all round.

Position one rectangle with a short side facing you, brush with egg yolk and sprinkle with a sixth of the chopped sage. Put a lamb fillet on the pastry close to the end facing you, then fold the long sides in to cover the ends of the meat; brush these with more egg yolk.

Freeze the lamb parcels on a tray until solid for 4 hours, then pack in a freezer container. Seal, label and freeze for up to a month.

To make the sauce, melt the redcurrant jelly in a pan over a gentle heat, add the port and rosemary and boil uncovered for 10-12 minutes until syrupy. Cool for 5 minutes, strain into a freezer container, then leave until completely cold. Seal, label and freeze for up to a month.

On the day defrost the lamb seam-side down on a wire rack for 3 hours at room temperature. Defrost the sauce at room temperature.

Preheat the oven to fan 200C/ conventional 220C/gas 7. Put the parcels seam-side down on a nonstick baking sheet, brush with egg yolk, then snip four incisions in the top of each. Bake for 25 minutes until golden. Remove from the oven and rest them for 5-10 minutes. Reheat the sauce in a pan.

Slice each parcel and serve with the sauce and watercress salad.