Wash fresh blackcurrants, remove any stems, and place the fruit (fresh or frozen) in a small saucepan with the sugar and water. Cover and gently bring to boiling point, then remove from the heat. When they have cooled a little, drain the blackcurrants, reserving the juice. Set the juice and the blackcurrants aside.
Heat the oil in a sauté pan and fry the pork fillets over a medium heat until golden all over. Season, then cover and cook for another 15 minutes. When cooked, remove them from the pan and allow them to rest.
Meanwhile, heat 10g of the butter in a saucepan and fry the apples gently for 10 minutes or until golden. Add the cinnamon.
Put the reserved blackcurrant juice and the jam in the pan the pork was cooked in, bring to the boil and simmer. Cut the remaining butter into pieces and whisk it in, simmering rapidly, until a glossy sauce is made. Add the blackcurrants.
Slice the pork fillets and serve on a bed of the sautéed apples, topped with the blackcurrant sauce.