Chicken, Mushroom and Pancetta Wellington

Place the bowl and blade of a food processor in the fridge or freezer for 30 minutes (or longer) to cool. They will need to be well chilled before use.

Preheat the oven to 180C/160C fan/ gas 4.

Lay the quartered mushrooms out on a baking tray and season with salt and pepper. Drizzle with olive oil and roast in the oven for 15-20 minutes until they are golden and have shrunk in size. Remove and leave to cool.

Square off the chicken breasts by trimming away the narrow bottom.

Remove the food processor bowl and blade from the fridge or freezer and blitz 130g of the chicken trimmings with 3 of the egg yolks and 1/2 teaspoon of salt for 1 minute until smooth.

By using a cold blade and bowl, you avoid cooking the chicken (the blade does become warm as it spins).

Remove the lid of the food processor and add the roasted mushrooms, chopped herbs, diced shallot, crushed garlic, breadcrumbs and mustard. Blitz for 30 seconds to break up the mushrooms and bring all the ingredients together. Lift out the blade from the bowl and scrape any of the mixture off it and back into the bowl. Transfer to a clean bowl and chill until required.

Prepare three sets of double layer of clingfilm on your work surface.

Carefully cut down the middle of each chicken breast to open it up - do not cut all the way through (you want to keep each breast in one piece).

The effect is to make a thinner layer of chicken, though it will be still be uneven in thickness at this point.

Lay down your first set of clingfilm on your work surface. Place slices of pancetta into two long rows, ensuring the slices overlap as you arrange them. Set aside.

Place another double layer of clingfilm on your work surface. Lay the butterflied chicken breasts flat on the clingfilm so they slightly overlap each other. Cover with another double layer of clingfilm and gently bash them with a rolling pin to make a large 20x25cm rectangle with an even thickness of 3-4mm. Remove the two top layers of clingfilm and evenly spread the chilled mushrooms stuffing over the surface. Carefully roll the chicken, using the clingfilm to help you and making sure you roll it tightly enough to keep the filling enclosed. Place the roll on the pancetta close to one long edge, and roll again to encase the stuffed chicken in the pancetta, finishing with the seal at the bottom.

Tightly wrap in clingfilm and chill in the fridge to firm up for 1-2 hours.

Preheat the oven to 220C/200C fan/gas 7. Put a baking tray in the oven to heat up - preheating it will help seal the base of the Wellington. Cut a piece of baking parchment to fit the tray which will be used during cooking (don't put the paper in the oven yet).

To finish the Wellington, brush the edges of the sheet of puff pastry lightly with some of the remaining egg yolk. Remove the clingfilm from the rolled chicken and place it on top, with the part where the pancetta slices are sealed facing upwards - the longest edge of the chicken roll should be towards the edge of the longest edge of the pastry. Roll the chicken in the pastry, ensuring the seal is on the bottom of the Wellington. Press the two ends of the pastry together at each end of the roll and use the back of a fork to seal completely. Turn the roll over, then brush the Wellington with the remaining egg yolk and transfer to the baking parchment. Allow the Wellington to come to room temperature for 30 minutes.

Lift the parchment and Wellington and place it on the hot tray, then bake in the hot oven for 15 minutes. Turn the tray in the oven, reduce the heat to 190C/170C gas/gas 5 and bake for a further 20-25 minutes.

Once cooked, remove from the oven and allow to rest for a minimum of 10-15 minutes before carving.