- Season each steak generously with salt and pepper.
- Bring the meat to room temperature before grilling.
- Fire up the grill – I used charcoal with a little bit of mesquite wood.
- Place the steaks on the hot part of the grill to sear, then move to a cooler area to cook evenly. Cook to an internal temperature of 128°F for medium rare.
- While the steak is cooking, butter the gill side of the mushroom with a teaspoon of the butter and sprinkle with salt and pepper.
- Place the mushroom gill side up on the grill and squeeze a little lemon over the mushroom cap. Grill until softened and lightly charred.
- Heat a cast iron skillet on the grill and add the rest of the butter and let it melt.
- Place the grilled mushroom cap in the skillet and chop it with a spatula into coarse pieces.
- Add chopped shallots and cook, stirring, until tender (about 3 minutes).
- Add Irish whiskey and broth and bring to a boil.
- Whisk the mustard and cream. Keep cooking and allow to thicken.
- Taste the sauce and season with salt, pepper, and lemon juice. Present the whole steaks on a platter with the sauce on the side.
- Carve the steaks at tableside and spoon sauce over each serving as desired. Enjoy!