For the demi glace: Preheat the oven to 400 degrees F. Place the veal bones with the onions, carrots and celery on a large sheet pan. Brush the bones with some tomato paste and cook 30 minutes.
Flip the bones and brush the other side with some tomato paste, then return the bones to the oven. Once the bones are crispy and dark, transfer with the vegetables to a large stock pot. Deglaze the sheet pan with red wine, adding all the browned bits and wine to the stock pot. Add the garlic, bay leaf, parsley and just enough water to cover the bones. Bring to a boil, then reduce the heat to a slow simmer for 12 to 14 hours.
Strain the stock, return to the pot and reduce the liquid over medium-high heat until it is as thick as you would like your demi glace to be.
For the gorgonzola reduction: Combine the cream, cheese and garlic in small saucepan, and reduce until thick, like gravy.
For the steak: Bring the steak to room temperature, at least 45 minutes or up to 1 hour 30 minutes for best results!
Sprinkle the steak generously with salt and pepper. Grill the steak to an internal temperature of 135 degrees F for medium rare (recommended) or desired doneness. Let steak rest for half the time it took to cook it.
For the mushrooms: Saute the mushrooms in a saucepan with the butter and some salt and pepper until tender, 2 to 3 minutes.
Serve the mushrooms over the steak along with the demi glace and gorgonzola reduction.
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.