Season brisket with salt and pepper (if you’re measuring, this is at least 1 teaspoon of kosher salt –I use Diamond Crystal– per pound of meat). Do this a few hours (up to 24) in advance, if you’re able (keep it uncovered in the fridge). It’s also fine just to season and go ahead and braise it right away, too.
Preheat oven to 275°. Heat canola oil in a large, heavy-bottomed dutch oven (at least 5.5qt)* over medium heat. Sear brisket fat side down first. Use tongs or any implement of your choosing to press the meat to encourage as much contact with the pot as possible.
Cook, without moving, until the fat side is deeply browned, 10–12 minutes (doing this over medium heat rather than medium-high will take longer, but with less risk of burning the rendered fat).
Using tongs or two large spoons, flip the brisket to brown on the other side, another 10–12 minutes. Be careful here, the fat is extremely hot and can splatter.
Transfer the brisket to a large plate or sheet pan and add the garlic and shallots to the pot, cut side down. Season with salt and pepper and cook, without moving, until the shallots and garlic are nicely browned, 3–5 minutes.
Return the brisket to the pot and add whatever broth or water you’re using (and Better Than Bouillon, if you’re using that), vinegar, worcestershire sauce, horseradish (if using) and bay leaves.
Bring to a simmer and place the lid on. Transfer to the oven and let it gently braise for 3–3 ½ hours.
Remove from the oven and make sure it’s done by inserting the tip of a knife into the thickest part– it should meet no resistance, the whole slab jiggling like jell-o.
To serve, transfer the brisket from the pot to a cutting board. Slice against the grain as thick or thin as you like and place on a large serving platter.
Give the juices a taste— they should be tangy, salty and very beefy with a bit of heat from the horseradish. Adjust with more worcestershire, vinegar or horseradish as needed.
Spoon the jammy shallots and garlic over the brisket along with the juices from the pot over the brisket. Serve with more horseradish on the side, along with some flaky salt and parsley, if you like.
