Make the cranberry sauce: put the redcurrant jelly, sugar and 200ml water in a small pan. Heat gently until the jelly has melted, then add the frozen cranberries and simmer for 8-10 minutes until the cranberries have burst and the sauce is syrupy, adding a little extra water if needed. Set aside.
Meanwhile, preheat the oven to 200°C, fan 180°C, gas 6. Heat the oil in a frying pan over a medium heat, then add the mushrooms and fry for 4-5 minutes until just tender and golden. Remove the pan from the heat and stir in the walnuts and chestnuts. Season with freshly ground black pepper.
Put the frozen Yorkshire puddings on a baking tray and pile in the mushroom filling (don’t worry if a little spills out).Top with the crumbled Stilton then bake for 8-10 minutes until piping hot and the Stilton has melted.
Meanwhile, steam the sprouts and carrots for 5-6 minutes until just tender. Serve with the Yorkshire puds drizzled with the cranberry sauce.