1 half venison loin (aka backstrap) for 3-4 people (about 1.25kg), the whole loin is about 2.5kg for a red deer.
Remove all fat and silver skin from loin
Tie the loin with butcher string to make it have a round cross-section (to make it less flat, so that it doesn’t over cook inside)
Preheat oven to 400F
Add a large piece of butter into a roasting pan, and heat the pan
Heat large skillet to medium high, with a little bit of oil
Fry each side of the loin for 2minutes, until nice and brown
Place the loin into the roasting pan, coat all sides with the melted butter
Roast for about 12-15 minutes until temperature is 140F (check after 8min, roll loin around in the butter)
Place on cutting board, cover with foil, let rest at least 10 min, then slice diagonally.
To make a sauce (one can just add cream to the bottom of the roasting pan to deglaze it, and that’s good enough). Or a sweet balsamic reduction:
Fry some shallots in the oil leftover in the skillet, deglaze with sweet balsamic, and then with some more liquid (e.g. stock, liquid from re-hydrating mushrooms, broth, etc). Reduce by about half, reserve.
Deglaze the roasting pan with the above liquid, add some cream, and reduce.