Season both sides of the steaks generously with salt and pepper. Be especially generous with the pepper.
Melt duck fat in a steel pan over medium-high heat. Add steaks; cook until firm and reddish-pink in the center for medium-rare, about 5 minutes per side. Sear the edges until browned, about 30 seconds each. Transfer steaks to a plate; let rest while you make the sauce. Turn off the heat.
Stir garlic into the same pan using a spoon. Add 1 teaspoon butter; let melt. Pour in bourbon. Heat until reduced to a sticky glaze, about 15 seconds. Add chicken stock. Bring to a boil over high heat while scraping up the browned bits at the bottom to deglaze. Cook until reduced by half, about 2 minutes. Add heavy cream; season with salt and cayenne pepper. Boil until thickened, 2 to 3 minutes.
Turn off heat and add remaining 2 teaspoons butter; swirl until melted, about 30 seconds more. Spoon sauce warm onto serving plates. Place steaks on top.