Slow-Cooker Spicy Buffalo Chicken Sandwiches

Ingredients

• 1 tablespoon extra-virgin olive oil
• 1 pound boneless, skinless chicken thighs, cut into 1 1/2-inch pieces
• coarse salt and ground pepper
• 1 pound boneless, skinless chicken breasts, cut into 1 1/2-inch pieces
• 1 medium yellow onion, diced small
• 3 garlic cloves, roughly chopped
• 1 medium red bell pepper, seeded and diced small
• 1 can (14.5 ounces) crushed tomatoes
• 1/4 cup hot-pepper sauce, such as frank's
• 3 tablespoons worcestershire sauce
• 2 tablespoons yellow mustard
• 1 tablespoon unsulfured molasses
• 8 hamburger buns