Step 1

Preheat oven to 350°F.

Step 2

Wash, dry, and shave parsley leaves off the stems; discard stems and mince the leaves. Place half of the parsley in a small bowl, along with pepper, and stir to combine. (Reserve remaining parsley for garnish.)

Step 3

Pat beef dry with paper towels and transfer to a roasting pan. Press parsley mixture into all sides of the beef.

Step 4

Cut garlic heads in half horizontally. Place in the center of a 12-inch square of aluminum foil, and drizzle with oil; fold foil around garlic to close the packet. Place in the roasting pan, alongside the beef.

Step 5

Place roasting pan in the oven and roast until a thermometer inserted into the thickest part of the beef registers 135°F (for medium-rare), 1 ¾ - 2 hours. (Remove garlic from the pan once it’s golden and very soft, 1 – 1 ¼ hours; set aside.)

Step 6

Remove beef from the oven and transfer to a cutting board. Loosely cover with foil and let rest, 15-20 minutes.

Step 7

Meanwhile, carefully open the foil packet and squeeze garlic cloves into a small saucepan. Using a fork, mash garlic into a smooth paste.

Step 8

Add broth and sherry to the saucepan with the garlic; stir to combine. Bring to a boil over high heat and cook until reduced by half, about 10 minutes.

Step 9

Add cream to the pan. Return to a gentle boil and continue to cook, stirring occasionally, until reduced by half, about 5 minutes. Remove from heat.

Step 10

Carve beef into thin slices. Garnish with reserved parsley and serve with roasted garlic sauce on the side.