Braised Brisket Street-Style Tacos

Ingredients

• 1 beef Brisket Flat Half (3 to 3-1/2 pounds)
• 1 tablespoon olive oil
• 1/2 teaspoon salt
• 1/4 teaspoon pepper
• 1 large onion, sliced
• 4 cloves garlic, minced
• 1 bottle (12 ounces) beer
• 1-1/4 cup tomatillo salsa, divided
• 16 to 20 small corn tortillas (about 6-inch diameter), warmed
• Chopped fresh tomatoes, chopped onion, chopped fresh cilantro or prepared pico de gallo (optional)