1. Heat oil in stockpot over medium heat until hot. Place beef brisket in stockpot; brown evenly. Remove brisket; season with salt and black pepper.
2. Add onion and garlic to stockpot; cook and stir 3 to 5 minutes or until onion is crisp-tender. Return brisket, fat side up, to stockpot. Add beer, chiles, broth and red pepper as desired; bring to a boil. Reduce heat; cover tightly and simmer 2-3/4 to 3-1/4 hours or until brisket is fork-tender.
3. Remove brisket. Skim fat from cooking liquid; keep cooking liquid warm. Trim fat from brisket. Cut into 4 to 6 pieces; shred with 2 forks. Stir shredded beef into reserved liquid.
4. Serve beef mixture in rolls topped with giardiniera, cheese and mayonnaise, if desired.
Roasted Red Pepper Mayonnaise: Place 1/2 cup jarred chopped roasted red pepper, 1/2 cup mayonnaise and 1 clove chopped garlic in food processor container. Cover; process until smooth. Yield: about 2/3 cup.
Test Kitchen Tips Brisket may be prepared a day ahead and refrigerated. To reheat, heat in stockpot over medium-high heat 9 to 14 minutes or until 165°F, stirring occasionally.