Cook and stir onion in butter and oil in a 10-inch skillet until tender. Stir
in broth, the 1/4 cup almonds, the ground red chiles, vinegar, sugar and cinnamon.
Heat to boiling; reduce the heat and simmer, uncovered, for 10 minutes.
Spoon mixture into a blender container, cover and blend on low speed until smooth,
about 1 minute. Return sauce to skillet. Dip chicken breasts into the sauce to coat
both sides. Place skin sides up in a single layer in the skillet. Heat to boiling
and then reduce the heat, cover and simmer until done, about 45 minutes.
Serve sauce over chicken and sprinkle with the remaining slivered almonds.