Allow steaks to sit at room temperature at least 20 minutes. Heat a cast iron skillet over medium heat and allow to get very hot, 5 to 10 minutes.

Brush oil over steaks, and season liberally with salt and pepper. Sear meat in pan and cook 3 to 4 minutes on one side or until nicely caramelized.

Turn down heat, flip meat over and cook an additional 4 to 6 minutes or until temperature reaches 120 - 125º.

Remove meat from pan to a dish and cover with foil or place in warm oven. Make pan sauce while steaks rest.

Using same pan, do not wipe or pour out any remaining fat or cooked bits. Set pan over medium-low heat.

Add shallots and mushrooms saute a couple minutes, it's ok if the pan is starting to stick some, add butter. Add sherry and turn up heat to medium, scrape up pan and reduce by 2/3. Add stock, bring to simmer, add demi glace and stir well to combine. Finish with cream.

Simmer until well thickened. Remove from heat, let stand briefly.

Season to taste. Serve sauce over steaks.