Pre-heat your oven to 200°C/400°F/Gas Mark 6 for 30 minutes.
Rub the iberico pork fillet with one tbsp of the oil, add some seasoning, then seal the outside of the meat all over in a hot frying pan until brown on all sides. Add the garlic cloves, fresh thyme and one tablespoon of butter and spoon the foaming butter all over the pork fillet until it is nicely coated. Place the pork in the oven and cook for 8 mins, basting the pork again halfway through. Remove from the oven, place the pork fillet, garlic and herbs in a warm plate, cover with foil and rest for 5 minutes.
To make the Pedro Ximenez sauce, use the same pan you have cooked the pork in but drain the cooking oil and let the pan cool down before you handle it. Add one tablespoon of butter and fry the chopped shallots and thyme gently, making sure you scrape all the caramelisation from cooking pork which is stuck to the pan. Add the Pedro Ximenez sherry, bring to the boil and reduce by half. Add the chicken stock and reduce by half again until the sauce is nice and syrupy. Check for seasoning and on a low heat, add the last tablespoon of butter mixing well until you have a glossy sauce. Do not boil the sauce after this or the butter will split.
To serve, slice your pork fillet and place on a warm plate, spooning the Pedro Ximenez sauce and serving with your choice of vegetables and potatoes.
