Heat oil in a large skillet over medium heat. Add garlic, onion, and chipotle. Cook for 3 to 5 minutes, or until onion is tender. Add chicken, tomato paste, adobo sauce, cumin and salt. Cook, stirring, for 2 to 3 minutes, or until chicken is well coated. Add beer and taco sauce and bring to a boil. Reduce heat to medium-low and cook uncovered for 15 to 20 minutes or until sauce has thickened.