1. Combine first 4 ingredients in a large bowl, stirring with a whisk. Gradually add olive oil, stirring constantly with a whisk. Add onion, cilantro, and coleslaw. Thinly slice 1 jalapeño half crosswise (keeping seeds), and remove seeds from remaining jalapeño halves. Cut the remaining halves into thin crosswise slices. Add the jalapeños to onion mixture, and toss well to coat. Cover and chill at least 1 hour.