Cut the fillet from the butcher of trust into strips.

Peel the onion and garlic and cut into small pieces.

Quarter the mushrooms lengthways and cut them down.

Fry the meat briefly in oil, flambé with cognac and remove.

Put the onion and garlic in the pan, add the mushrooms a little later; fry over medium heat.

Add the mustard (here it was Thomy BBQ) and very little water.

Put the meat back in the pan, mix everything together.

Season to taste with pepper and salt.