Season both sides of the filets with salt and pepper.
Place the filets on the grill at a 45 degree angle to establish nice grill marks. Once the filet reaches an internal temperature of 125 to 130 degrees for medium-rare, remove the steak from the grill and let rest about 5 minutes before serving.
Plate each filet with the Cabernet Peppercorn Demi-glace and your favorite side dishes.
In a saucepan over medium heat, saute mushrooms, shallots, and peppercorns in oil. When shallots are tender, deglaze with red wine and reduce by two-thirds.
Whisk together the reduction and demi-glace until smooth.
Whisk in the cream and beef base.
Combine a few teaspoons of cornstarch (or more as needed) with a little cold water to make a slurry.
Add slurry to the sauce to thicken; cook for 1 minute and then remove from the heat.