Notes: If making sauce ahead, chill airtight up to 1 day. Or freeze up to 1 month. Thaw sauce, whirl smooth in a blender, then reheat.
1. In a 10- to 12-inch frying pan over medium heat, frequently stir onion, roasted pepper, garlic, butter, and cumin until onion is limp, 6 to 8 minutes.
2. Whirl mixture in a blender or food processor with broth and chipotles.
3. Scrape purée back into frying pan. Add cream and stir often over high heat until simmering, about 3 minutes.