1. Cook bacon in a large skillet over medium heat until crisp and fat has rendered. Transfer bacon to a paper-towel-lined plate and set aside. Remove and discard all but 1 tablespoon of bacon fat from the skillet. Reduce heat to low; add olive oil, vinegar, lemon juice and sugar. Cook, stirring, until sugar has dissolved and dressing is well combined.

2. Combine frisee, parsley, and celery in a large bowl; season with salt and pepper. Toss salad with dressing and reserved bacon; serve immediately.