Nothing fancy or elaborate, just canned Chipotle in adobo sauce brings the flavor and slow cooker does the rest.
Add the onions, peppers, garlic, and chicken into the slow cooker, season with a dash of salt and brown sugar.
Blend the can of chipotle in adobo sauce and keep it handy. When chicken is part-way cooked, say after an hour or so in the slow cooker, add enough the chipotle sauce (to taste) and slow cook for another hour or till chicken is cooked through and the flavors meld.
Serve with fresh home-made corn tortillas or naan or home-made flour-tortillas or even brown basmati rice.