Per Vegetarian Times, "Many Irish salad dressings are called cream dressings because they include lots of cream. Here, we’ve lightened the sauce and added whole-grain mustard and buttermilk for extra tang."
Place eggs in medium saucepan and fill with water to cover eggs by 2 inches. Bring to a boil, remove from heat, and cover saucepan with lid. Let eggs sit 10 minutes, then remove with slotted spoon and place in bowl of cold water. Remove shells when cool.
Bring water back to a boil, and add asparagus. Cook 2 to 3 minutes, or until bright green. Rinse under cold water, and pat dry. Cut into 1/2-inch diagonal slices.
To make Dressing: Place shallots, mustard, vinegar, and sugar in small bowl, and stir to combine. Season with salt and pepper. Whisk in mayonnaise and buttermilk until smooth.
To assemble Salad: Lay butter lettuce leaves on 2 large plates followed by asparagus, watercress, cucumber, and radishes. Slice eggs into quarters, and arrange on top of Salad. Drizzle 2 Tbs. dressing over each serving.