Combine all the ingredients in a bowl or a quart-size jar. Add 1/4 cup of cold water. Whisk the mixture in the bowl or shake the jar up until the ingredients are well blended. Refrigerate.
When ready to serve, combine the cheeses and the chopped parsley on a bowl or jar. By hand, tear up leaves of a head of romaine and a head of Boston or Bibb or butter lettuce. (Feel free to add other kinds of greens, but stay away from bitter greens like endive or radicchio.)
Toss the salad with about two-thirds the amount of dressing your instincts tell you, and with a little bit more cheese mixture than you were considering. Add more dressing or cheese to taste.