I was just now browsing Martha Stewart's website and saw that she has a serrano vinaigrette recipe! I can't vouch for it, but Martha's recipes are always delicious. Here it is:
Ingredients
2 serrano or jalapeno peppers, seeded and deveined
6 tablespoons red-wine vinegar
1 tablespoon honey
3/4 teaspoon salt
1/4 teaspoon freshly ground black pepper
9 tablespoons extra-virgin olive oil
Directions
1.Mince the serrano peppers. Combine half of the minced pepper, vinegar, honey, salt, and black pepper in a blender. Process until serrano pepper has been fully blended. With machine running, add olive oil until combined and mixture is thick. Use the remaining minced serrano pepper as a garnish.
Thought I'd add the link:
http://www.marthastewart.com/344893/serrano-vinaigrette