Do not trim the fat from the tenderloin as this will help to keep it moist.
Slice it in half lengthways, batter the 2 halves with a rolling pin to flatten and widen them slightly, then season with salt and freshly milled pepper. Next, to prepare the stuffing, melt the butter in a medium frying pan and fry the onion gently over a medium heat for 10 minutes or until softened, then stir in the herbs and mushrooms and raise the heat slightly.
Cook for 3 or 4 minutes then transfer the contents of the pan to a bowl. Lightly beat the egg with the cream and add this, along with the remaining stuffing ingredients, to the bowl. Fork the mixture together lightly, taste and season. Now pat the stuffing on to one half of the tenderloin, and replace the other half on top. Smear the fillet with the softened butter and season with freshly milled pepper. Then lay the bacon on top of the fillet to cover it. Tie the fillet round with string at about 2 inch (5 cm) intervals to hold the whole thing together, slip a long palette knife under its length and transfer to the buttered roasting tin.
Bake in the top half of the oven for 1 hour. Then transfer the fillet to a dish to keep warm and now make the gravy. Place the tin over direct heat and sprinkle in the flour to soak up the juices, stirring vigorously with a wooden spoon. Then, when it’s smooth, gradually add the wine, switching to a balloon whisk to whisk everything together and then let the gravy bubble till syrupy.
Serve the pork, cut into thick slices, with the gravy poured over, and perhaps a garnish of fried apple rings. To make these, core but do not peel the apples, then cut them into rings and fry gently in the butter in a large frying pan until tender.
Pre-heat the oven to gas mark 4, 350°F (180°C).
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