Place the garlic, shallot and Serrano in a food processor. Pulse to mince. Add the herbs and vinegar. Pulse to chop. Spoon into a bowl. Stir in the olive oil and sea salt. Let rest for 1 hour. Store in refrigerator for up to two weeks.
You can cook all of this on a stovetop or gas grill, too. You just won't get the same smoky flavor.
Reduce the bite you get from raw onions by soaking the slices in ice water for 30 minutes.
You can use kosher or table salt instead of sea salt.
Go all out and serve it with a glass of Malbec wine from Argentina.