- 1 (31/2- to 4-lb) boneless beef brisket, trimmed of excess fat
- 3/4 teaspoon salt
- 1/2 teaspoon black pepper
- 2 tablespoons olive oil
- 2 pound onions, halved lengthwise and thinly sliced lengthwise (6 cups)
- 1 Turkish or 1/2 California bay leaf
- 1 (12-ounce) bottle beer (not dark)
- 1 dried-porcini bouillon cube (less than 1/2 ounce) or 1 beef bouillon cube, crumbled
- 1 tablespoon balsamic vinegar
- Preheat oven to 350°F.
- Pat brisket dry and sprinkle with salt and pepper. Heat oil in a 6- to 8-quart wide heavy pot over moderately high heat until hot but not smoking, then brown meat well on all sides, about 10 minutes total. Transfer with tongs to a platter.
- Cook onions with bay leaf in fat remaining in pot over moderate heat, stirring occasionally, until golden, 10 to 12 minutes. Remove from heat and transfer half of onions to a bowl. Arrange brisket over onions in pot, then top with remaining onions. Add beer, bouillon cube, and vinegar (liquid should come about halfway up sides of meat) and bring to a boil.
- Cover pot and braise in middle of oven until meat is very tender, 3 to 3 1/2 hours. Cool in sauce, uncovered, 30 minutes.
- Transfer brisket to a clean cutting board. Skim off any fat from sauce, then season with salt and pepper. Slice meat across the grain and serve with sauce.