Preheat the oven to 200°C.
Brown the venison in a hot frying pan with rapeseed oil and season with salt and pepper.
Transfer the meat to a roasting tray and roast for five minutes.
Lower the oven temperature to 180°C, add butter and sage, and roast for an additional 10 minutes while basting frequently.
Remove the meat from the oven and set it aside in a warm place to rest.
Set the oven to 160°C.
Blanch the endives in boiling salted water, drain, and place into an ovenproof dish.
Pour stock over the endives, add butter, and bake for 30 minutes.
Squeeze excess liquid from the cooked endives and cut them in half lengthways.
Caramelise the endives cut-side down in a hot pan with oil for 3 minutes.
Prepare the sauce by browning venison trimmings and vegetables in oil.
Add wine and stock to the trimmings and simmer until the liquid reduces by half.
Strain the sauce into a clean pan and whisk in the butter until smooth.
Carve the venison and serve with the endives, sauce, and chive garnish.