While your oven preheats to 350°F, combine salt, paprika, pepper, thyme, and oregano in a small bowl to create your spice rub. Simultaneously, pour 1 cup of hot water over the dried porcini mushrooms in a separate bowl and let them steep for 20 minutes—this softens them and creates an incredibly flavorful liquid you'll use in the braising sauce. I find smoked paprika and freshly ground pepper make a real difference in the depth of flavor here, so don't skip quality ingredients if you can help it.

Pat the brisket dry with paper towels, then generously rub the spice mixture all over both sides of the meat, pressing gently so it adheres. Heat the olive oil in a large, heavy-bottomed Dutch oven or braising pan over medium-high heat until it shimmers. Once hot, carefully place the brisket in the pan and sear for 6 minutes on the first side without moving it—this creates a flavorful crust. Flip and sear the other side for 4 minutes until deeply browned. Transfer the meat to a cutting board while you build the braising liquid.

Drain the rehydrated mushrooms, carefully reserving the steeping liquid (watch for any grit at the bottom). Chop the softened mushrooms into bite-sized pieces and set aside. In the same pan where you seared the brisket, pour in the vermouth, chicken stock, and the reserved mushroom liquid. Simmer for 2 minutes while scraping up all the browned bits stuck to the bottom of the pan with a wooden spoon—these flavorful bits (called fond) are liquid gold for your sauce. Stir in the diced tomatoes, bay leaves, and chopped mushrooms.

Return the seared brisket to the pan, nestling it into the braising liquid. Scatter the sliced onions over the top of the meat and sprinkle the minced garlic evenly across the surface. Bring everything to a boil on the stovetop (about 2-3 minutes), then transfer the entire pan to your preheated 350°F oven. Roast uncovered for 30 minutes, then cover tightly with foil and continue braising until the brisket reaches an internal temperature of 200°F, which should take 2 to 2.5 hours. I like to check the temperature at the thickest part of the meat—this tenderness indicator tells you the collagen has properly broken down.

Once the brisket reaches 200°F, carefully transfer it to a cutting board and tent loosely with foil to rest for 10 minutes—this keeps the meat incredibly juicy when you slice it. Leave the pan of braising liquid and vegetables on the stovetop over medium-high heat and simmer for 10-15 minutes to concentrate the flavors and reduce the sauce slightly. Remove the bay leaves with a spoon or tongs, then use a ladle or shallow spoon to skim off any excess fat that has risen to the surface. Stir in the brown sugar to balance the acidity and deepen the flavor.

Slice the rested brisket against the grain into your desired thickness (about 1/4-inch slices work beautifully for a grilled cheese). Arrange the slices on a serving platter or individual plates, then spoon the onions, mushrooms, and rich braising sauce generously over the top. Serve immediately while everything is warm, with crusty bread on the side for soaking up that incredible sauce, or use these slices as the star filling in a gourmet grilled cheese sandwich.