3 romaine hearts (1 pound), torn into bite-size pieces
1 Hass avocado, cut into 1/2-inch dice
3/4 cup grape tomatoes, halved
1 1/2 ounces Maytag blue cheese, crumbled (1/3 cup)
In a large bowl, whisk the sherry vinegar with the mustard. Gradually whisk in the olive oil until incorporated. Add the cocktail onions and season with salt and pepper. Add the remaining ingredients, toss well and serve.