Creamy Pancetta Dressing by M. Chiarello

Ingredients
3 tablespoons olive oil
1 1/2 cups roughly cut pancetta
1 onion, finely chopped
1 clove garlic, minced
2 tablespoons minced fresh thyme leaves
1/4 cup cider vinegar
1 cup mayonnaise
1 cup sour cream
Freshly ground black pepper
3 heads iceberg lettuce, quartered and cleaned

Directions
Heat a saucepan over medium-high heat. When the pan is hot, add the olive and heat. When the oil is hot, add pancetta and saute, and caramelize for about 10 to 15 minutes. Stir onion into mixture, toss and saute for another 10 minutes, until the onion begins to brown. Add garlic, thyme, and cider vinegar, and remove from heat. Allow mixture to cool for about a 1/2 an hour.