Ingredients

• 1 yolk from a large hard-boiled egg
• 2 3/4 teaspoons white-wine vinegar
• 1 teaspoon Dijon mustard
• 1/4 teaspoon salt
• 1/8 teaspoon black pepper
• 1/4 cup olive oil
• 16 cups loosely packed mâche (lamb's lettuce; see above)

Instructions

1. Crumble yolk into a blender, then add vinegar, mustard, salt, and pepper and blend until combined well. With motor running, add oil in a slow stream, blending until combined well.
2. Toss mâche with vinaigrette just before serving.