Preheat to 350 degrees.

Season meat with salt and pepper and then mix together rosemary and garlic. Set it aside.

Heat up a skillet with cooking oil and sear all side of the meat. Remove the roast from the pan and coat the meat with the herb-garlic mixture.

Transfer the meat back to the roasting pan and roast in the preheated oven until medium-rare, (about 14 minutes per pound for bone in and 8 mins per pound for no bones)

In a medium pan, saute the mushrooms with butter until cooked through and then season with salt and pepper.

Remove the meat from the skillet it was cooked in and bring the pan to the stovetop. Add stock to the pan and deglaze it, being sure to scrape the bits on the bottom. Allow to simmer until thick.

Add the mushrooms to the sauce and serve the roast sliced with accompanying mushroom sauce. Garnish serving platter with fresh rosemary if desired.