2 x 500 g packets all butter puff pastry , chilled
Preheat the oven to 180°C/350°F/gas 4. Place the turkey breast upside-down on a board. Gently slice into the natural join of the breast muscle to open it out and make a sort of pocket. Season well and drizzle with olive oil. Sprinkle over half the thyme leaves, then spread over an even layer of cranberry jam, pushing it into all the nooks and crannies. Fold it back into shape to seal the mixture inside – swiss roll-stylie – and push a few cocktail sticks into the seam to keep it together. Transfer the turkey to a roasting tray, season the outside with the remaining thyme leaves, a good pinch of salt and pepper and a drizzle of olive oil. Rub it all over, cover in tin foil and roast in the hot oven for 60 to 70 minutes, or until just cooked through – using a thermometer, you want it to be 72°C at the thickest point.
Meanwhile, soak the porcini in a dish of just-boiled water. After 5 minutes, stir with a fork so any bits of grit sink to the bottom. Add the bacon to a large frying pan with a splash of oil on a medium heat and fry for 5 to 10 minutes, or until beautifully golden and super crispy. Strip in the leaves from 2 rosemary sprigs for the last 30 seconds or so. Remove everything from the pan with a slotted spoon and set aside, leaving the bacon fat behind. Add the fresh mushrooms to the pan with a pinch of salt and pepper. Drain and chop the porcini, saving the water, then stir into the pan. Add a splash of the water, avoiding the grit, then cook for around 10 to 15 minutes, or until the pan starts to sizzle again and the mushrooms are golden, soft and sticky with caramelly edges.
To make the gravy, cut the thigh off the turkey leg and slash into it slightly. Throw the leg and thigh into a pot along with the carrot, leek and onion. Stir in the flour, add a good pinch of salt and pepper and 2 litres of boiling water. Add a heaped tablespoon of cranberry jam, the balsamic vinegar and remaining rosemary sprig. Bring back to the boil, then reduce to a simmer for around 2 hours, or until thick. Strain it through a sieve and reheat before serving.
When the mushroom pan is dry, add a knob of butter and toss to coat. Tip the mushrooms into the food processor and whiz until you get a good mixture of smooth and chunky. Leave to cool. Once the turkey breast and stuffing have cooled, you can get on with assembling the wellington.
Dust a clean surface with flour, then roll out each packet of puff pastry to the size of a shoe box (one will be the base, one the lid – roll the lid ever so slightly bigger). Line a large roasting tray with greaseproof paper, dust with flour, then add the smaller piece of pastry. Spread half of the mushroom stuffing onto the middle of the base to cover an area the same size as your turkey breast. Remove the cocktail sticks, then place the turkey breast on top and spread the remaining stuffing over the top packing it all in and smoothing it out so that the whole breast is covered. Sprinkle with the crispy bacon and rosemary, then brush the edges of the pastry with beaten egg. Lay the second sheet of pastry over the top, gently mold it round the shape of the breast, pushing all the air out and seal together. Trim the edges to around 4cm, then pull, twist, tuck and pinch in the pastry (like in the picture).
Brush the whole thing with beaten egg then all the hard work’s done. Leave it uncovered in the fridge overnight until you’re ready to cook. On Christmas day, cook at 180°/350°F/gas 4 for 50 to 60 minutes, or until risen, puffy and beautifully golden and the turkey is piping hot throughout. Remove from the oven and leave to cool for around 10 minutes before carving. Serve carved into 2.5cm with the gravy and all the usual. Christmas in a mouthful.