In a small bowl, stir together the 2 teaspoons salt, 3 tablespoons pepper, and dry mustard. Sprinkle the mixture evenly over both sides of the steaks, pressing it into the meat with your hands.

In a deep frying pan over medium-high heat, melt the butter with the olive oil. Add the filets and cook for 2 minutes. R.educe the heat to medium. turn the filets, and cook for 2 minutes longer.

Continue to cook, turning the steaks every 2 minutes, until done as desired, about 6 minutes longer for rare, 8 minutes longer for medium-rare, and 10 min­utes longer for well done. Transfer the steaks to a platter and tent with aluminum foil to keep warm.

Add the garlic and the onion to the pan over medium heat and cook, stirring occasionally, until the onion is soft, about 5 minutes. Add the bourbon (being careful, as the pan might flame), and deglaze the pan, scraping any browned bits on the pan bottom. Add the water and the beef stock and simmer until reduced by half, about 5 minutes.

Add the thyme and the sour cream and cook, stirring, for 1 minute. Stir in the Dijon mustard and any accumulated juices from the cooked steaks. Add the hearts of palm and heat through, about 1 minute. Season with salt and pepper.

Spoon the warm sauce over the steaks. Garnish with the tomatoes and serve at once.