30 cascabel chiles, stemmed
1 1/3 cups cider vinegar
2 tablespoons mined onion
1 tablespoon minced garlic
For a milder purée, rub chiles between your palms to remove most of the seeds.
Chop chiles coarsely with a knife or in a food processor. Put them in a bowl and pour the vinegar over. Cover and refrigerate overnight.
Add onion and garlic to the chiles and either cover the bowl with plastic and microwave on HIGH for 1 minute, or put them in a saucepan over medium-high heat, cover, and simmer for 3 minutes.
Let cool slightly, then purée in a blender until very smooth. Let cool.
Store in an airtight container for up to 1 month.