Lightly coat the tenderloin in flour, then shake off any excess.
Heat butter and oil in a pan over medium-high heat.
Sear the floured tenderloin for 2 minutes per side until browned.
Add cognac to the pan and flambé carefully.
Remove the meat from the pan and set aside.
Toast the green peppercorns in the same pan for 1 minute.
Add mustard, cream, and beef stock to the pan and stir to combine.
Return the meat to the pan and baste with the sauce for about 3 minutes.
Remove the meat again and let it rest.
Let the sauce simmer and thicken slightly, then pour over the plated meat and enjoy.
