Place the venison in a dish with three tablespoons of olive oil, balsamic vinegar, carrot, and onion.
Season with salt and pepper and marinate in the fridge overnight.
Heat a non-reactive frying pan and fry the sliced onions in butter for 3 minutes until softened.
Add the morels to the pan and cook for 10 minutes.
Add the porcini mushrooms and fry for another 5 minutes.
Stir in the aged balsamic vinegar, sherry, and cream, then simmer for 10 minutes.
Adjust the thickness with soaking water and season to taste.
Remove the venison from the marinade, pat dry, and season with salt and pepper.
Fry the venison steaks in two tablespoons of olive oil for 4 minutes per side.
Serve the venison on top of the sauce and finish with optional truffle shavings.