In a small bowl whisk together cornstarch, cumin, salt, pepper, smoked paprika, chili powder, garlic powder, onion powder, brown sugar, cayenne, beer and tomato paste.

Add the chicken to a slow cooker, pour the beer mixture over the chicken.

Cook on low for 6 hours or until chicken is cooked through. Stir at least once during cooking.

Spoon chicken into tortillas

Note: if you use chicken breasts, shred in the slow cooker with two forks and allow to sit in the slow cooker, uncovered for about 15 minutes before serving.