Char each of the peppers over a gas flame or barbecue for 3-5 min until blackened on all sides. Place in a large bowl and cover tightly with plastic wrap for 10-15 minutes until softened. Peel away and discard skins. Remove cores, open each pepper and scrape out the seeds. (If you have sensitive skin, use gloves when handling chilis.) Transfer to work bowl of a food processor.
Heat oil in a skillet. Add onions and sweat 10 minutes until soft and translucent and just beginning to color. Add to food processor.
Pulse food processor until desired consistency is achieved. Return to skillet.
Add bay leaves, rosemary, balsamic vinegar, brown sugar, cinnamon stick, salt and pepper and stir. Simmer over low heat 30 minutes until thick and jammy. Remove and discard bay leaves and cinnamon stick. Cool thoroughly and store in the refrigerator.