Pulled Chicken Sandwiches With Pickled Onions

Name: Pulled Chicken Sandwiches With Pickled Onions
Ingredients: 3 cups ketchup; 1 cup beer; 1/2 cup maple syrup; 1/2 cup honey; 1/2 teaspoon red pepper flakes or 1-2 teaspoons hot sauce; 2 tablespoons light brown sugar; 2 tablespoons red wine vinegar; 4-5 lb boneless, skinless chicken thighs; 2 cups chicken broth; 2 tablespoons olive oil; 1/4 cup barbecue sauce; 30 mini brioche rolls or 10 brioche rolls; 1/2 cup sugar; 3 cups red wine vinegar; 1 teaspoon whole cumin seeds; 1/2 cup olive oil; 1 teaspoon salt; 1 teaspoon freshly ground pepper; 2 red onions, thinly sliced