Heat large skillet over medium high-heat, 2-3 minutes
Quarter and thinly slice 1 3/4 white onion
Remove longaniza from casing and add to pan, breaking into small, pea-sized pieces. Stir occasionally and allow to brown and the meat to release its grease, 5-7 minutes
Add oil, raisins and sliced onions. Fry until onions are golden, 8-10 minutes, stirring occasionally
Meanwhile, blend broth, tomatoes, remaining 1/4 onion, garlic, chipotles in blender until smooth
Add chicken and sauce from previous step to pan once the onions are golden, stir to incorporate
Reduce heat to medium and allow to simmer uncovered until liquid is reduced, about 8-10 minutes
Add salt to taste