I saw this recipe on the Rachael Ray show and it is delicious! It is a combination of French dip sammy and French onion dip. Be sure that the onions are well-carmelized, the sweetness is really worth the wait!
Cut about a quarter of an inch off the top of the garlic head and place it onto a square of aluminum foil. Drizzle with about 1 tablespoon extra virgin olive oil and close the foil up around the garlic. Transfer to the oven and roast until golden brown and tender, about 40 minutes. Remove from the oven and let cool.
While the garlic is roasting, place a large skillet over medium heat with 1 turn of the pan of olive oil, about 1 tablespoon, and the butter. Add the onions, bay leaf and thyme to the pan and cook gently until the onions are well caramelized, about 30 minutes. Season with salt and pepper, and reserve.
When the garlic is cool enough to handle, place a medium pot over medium-high heat with the beef stock. Squeeze the roasted garlic cloves out onto a cutting board, mash it into a paste with your knife and whisk it into the warm beef stock.
To assemble the sammies, dip the roast beef slices into the roasted garlic jus. Divide the meat between the four rolls and top each with some of the caramelized onions. Serve with additional jus on the side for dipping.