Heat oil in stockpot over medium heat until hot. Place beef brisket in stockpot; brown evenly. Remove brisket; season with salt and black pepper.
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.
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.
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.
Nutrition information per serving: 375 Calories; 90 kcal Calories from fat; 10 g Total Fat; 3 g Saturated Fat; 4 g Monounsaturated Fat; 62 mg Cholesterol; 687 mg Sodium; 26 g Total Carbohydrate; 2.7 g Dietary Fiber; 40 g Protein; 4.2 mg Iron; 7.1 mg Niacin; 0.4 mg Vitamin B6; 2.6 mcg Vitamin B12; 8.6 mg Zinc; 36.8 mcg Selenium;