1 Preheat the oven to 180oC, gas mark 4. Trim the venison and remove the bones to form a venison loin. Lightly season, then heat a large frying pan over a medium heat and add a little sunflower oil.
2 Sauté the meat until brown with a caramelised crust all over then reduce the heat and add 20g of the butter. Roll the meat in the butter and oil mixture. Cover and let the meat cook to medium rare, about 20-23 minutes (the venison will be dry and tough if overcooked), taking care not to burn the pan. When the meat is cooked, remove it from the pan and set onto a warm plate to rest.
3 Place the cubed root vegetables into a roasting dish, with the garlic cloves and thyme, all drizzled with olive oil and seasoned, and roast for about 40 minutes in the preheated oven, turning half way through.
4 Discard the fat from the venison pan then return the pan to a medium heat, add the port and redcurrant jelly and stir to pick up any caramelised meaty bits from the base. Add the chicken stock and stir well to make a sauce, finishing with the remaining 10g butter whisked in. Keep warm.
5 For the rumbledethumps, peel and cut the potatoes into even chunks then cook gently in boiling salted water for 10-15 minutes until tender. Turn off the heat and drain the potatoes before returning to the pan. Leave for a minute over a low heat to allow excess water to evaporate, then mash. Add the butter and cream and beat in the blanched Savoy cabbage, salad onions and seasoning. Keep hot.
6 Cook the kale in a butter emulsion (water and butter) in a pan with a lid for about 5 minutes, until tender. Season.
7 Serve the meat sliced on top of the roasted veg, with a quenelle of rumbledethumps on the side plus the kale. Pour the sauce over the meat and dot around the plate.