- 1 1/2 tablespoons fresh lemon juice
- 1/4 teaspoon Dijon mustard
- 3/8 teaspoon salt (preferably fine sea salt)
- 1/8 teaspoon black pepper
- 1/3 cup extra-virgin olive oil
- 2 hearts of romaine, trimmed, quartered lengthwise, then sliced crosswise into 1/4-inch strips (8 cups)
- 3/4 lb Bibb lettuce (3 medium heads), trimmed, quartered lengthwise, then sliced crosswise into 1/4-inch strips
- Whisk together lemon juice, mustard, salt, and pepper in a small bowl, then add oil in a slow stream, whisking until emulsified.
- Toss lettuces with just enough dressing to coat.