Pat beef fillets with paper towel to remove excess moisture, and press crushed peppercorns and sea salt evenly into meat so that both sides are covered
Heat a cast iron pan or heavy bottomed frying pan over high heat until hot, and add olive oil and butter
Place steaks in pan, and cook for 5 minutes per side
Remove steaks from pan, place on a platter, and cover with foil
Add bourbon to pan, and stir to deglaze and loosen up browned bits
Add the beef stock, mustard and heavy cream, stir, and cook until sauce is thickened
Return steaks to pan, stir in any juice from platter, and spoon sauce over steaks
Serve immediately for medium rare steaks, or simmer until temperature reaches 160 degrees, according to meat thermometer, and serve