Trim the fat from the beef, and cut the beef into strips. Put the beef, onions, fennel, and roasted garlic into a large braising pan. Season the mixture with salt, and pepper. Pour the beer over the ingredients in the pan, submerging them. Cover the pan tightly with two layers of aluminum foil. Cook the stew in the oven for 8 hours. Transfer the stew to bowls, and garnish with fennel fronds.
Preheat the oven to 300 degrees F.
Cut the heads of garlic in half and sprinkle with extra-virgin olive oil, salt, and pepper, to taste. Wrap the heads in aluminum foil, and bake for 40 to 45 minutes.