Pat the meat dry and pierce it all over on both sides with the tip of skewer or small, sharp knife tip.
In a large (2 gallon) resealable plastic bag, combine 3 quarts of icy water, the bay leaves, orange, Worcestershire sauce, parsley and black pepper. Bring the remaining 1 cup of water to a boil and add the salt to dissolve. Add salt water to the icy brine. Add the meat, then remove all the air and seal the bag. Place on a tray in the fridge and weigh the meat down under a second tray to keep it submerged. Refrigerate for 1-2 days.
To cook, remove the meat from the brine and pat dry. To a Dutch oven over medium-high heat, add the olive oil and meat and brown the brisket on all sides. Remove the meat to a plate and add butter (or olive oil) to the pan, to melt. Once it foams, add the onions, thyme and chicken stock. Bring to a bubble and add the brisket back. Cover, then reduce the heat to low and simmer for 2 1/2 hours. During the last 45 minutes of cooking, add the whole carrots, then cover and keep cooking.
For the gremolata, on a large cutting board, finely chop the orange zest, parsley, carrot tops and toasted almonds together.
Remove the vegetables to a warm platter, then slice the meat and top with the stock to keep moist.
Serve topped with gremolata.