Place the corned beef briskets into a large pot. Sprinkle in one of the spice packets, and discard the other one or save for other uses. Pour in the beer, and fill the pot with enough water to cover the briskets by 1 inch. Add the bay leaves, peppercorns and garlic cloves. Cover, and bring to a boil.
Once the liquid comes to a boil, reduce the heat to medium-low, and simmer for 4 to 5 hours, checking hourly, and adding more water if necessary to keep the meat covered.
Carefully remove the meat from the pot, as it will be extremely tender. Set on a cutting board, and allow it to rest until it firms up a bit, about 10 minutes. Slice or shred to serve. I discard the cooking liquid, but it can be used to cook cabbage and other vegetables if desired.