Brown the veal cubes in a little unsalted butter until the pieces are lightly golden.

Sprinkle with 2 tablespoons of flour. Stir well. Add 2 cups of water, the vegetable bouillon cube, the wine, and season lightly with salt and pepper. Stir.

Slice the carrots into rounds and thinly slice the onion, then add them to the meat along with the mushrooms.

Simmer over very low heat for about 1 1/2 to 2 hours, stirring occasionally. Add more water if needed during cooking.

In a bowl, mix the crème fraîche (or sour cream) with the egg yolk. Add this mixture to the meat at the very end, stir well, and serve immediately.