Sturgeon, mashed mushrooms and gravy

Ingredients for the sturgeon confit:
- 100 g Riofrío sturgeon
- 80 g mushrooms
- 100 ml milk
- Extra virgin olive oil
- Salt
- Black pepper
Ingredients for the gravy(* large quantities used for the base):
- 500 g beef bones
- 2 carrots
- 1 onion
- 2 tomatoes
- 1 l red wine
- 2 l water
Preparing the sturgeon confit:
- Heat oil in a pan to 60ºC. Add the sturgeon loin. Cook for 12 minutes letting it confit slowly.
- Clean the mushrooms well and cut into small dices.
- Salt and sauté in a little oil. Add the milk and a pinch of salt and bring to a boil.
- Once it is boiling, mash until obtaining a homogenous puree and add a pinch of pepper.
Preparing the gravy:
- Chop all ingredients and bake in the oven at 250ºC with a dash of oil.
- When brown, remove from the oven, place in a pot, and deglaze with the wine.
- Add water and boil for six hours over medium heat. Let it reduce until a dark sauce is obtained. That will be our gravy.
- On a plate place the mashed mushrooms first followed by the sturgeon. Dress with the gravy.