Mix all ingredients in a small bowl, set aside.

Rub brisket all over with spice rub, set aside. NOTE: If you can, cover and chill for at least 2 hours or overnight. Let stand at room temperature for 1 hour before continuing. I didn't do this, and the beef still had a great flavor.

Preheat oven to 325°F.

Heat 1 tablespoon oil in a large wide pot over high heat. Add brisket, fat side down. Cook undisturbed until well browned, 5 to 6 minutes. Turn brisket over and cook until browned, about 3 minutes. Using tongs, transfer to a plate.

Reduce heat to medium and add remaining 1 tablespoon oil. Add onion and garlic. Cook, stirring occasionally, until onion is slightly golden, about 5 minutes.

Add broth and all remaining ingredients. Bring liquid to a simmer. Return brisket to pot. Cover and transfer to oven.

Braise until brisket is very tender to the touch but still holds its shape, about 4 1/2 hours. Using a large spatula, transfer brisket, fat side up, to a large plate.

Strain braising liquid into a large bowl. Return liquid to pot, bring to a simmer, and cook until reduced to 2 cups, about 15 minutes.

Score fat side of brisket by cutting a crosshatch pattern of 1/4"-deep slits spaced 1/2" apart.

Transfer 1/4 cup braising liquid to a bowl, and add jam and bourbon and whisk together, until smooth. Season with salt and pepper.

Preheat broiler.

Line a baking sheet with foil, and place the brisket on it. Baste, or spoon, the beef with the peach jam mixture, generously. Broil brisket in pot until browned and glazed, watching carefully to prevent burning, 4 to 5 minutes.