Preparation Separate endive leaves, then thinly slice lengthwise and transfer to a large bowl. Whisk together vinegar, chives, mustard, 1/4 teaspoon salt, and 1/8 teaspoon pepper in a bowl, then whisk in oils in a slow stream until emulsified. Toss endive with enough vinaigrette to lightly coat. Season with salt and pepper.
Preparation Separate endive leaves, then thinly slice lengthwise and transfer to a large bowl. Whisk together vinegar, chives, mustard, 1/4 teaspoon salt, and 1/8 teaspoon pepper in a bowl, then whisk in oils in a slow stream until emulsified. Toss endive with enough vinaigrette to lightly coat. Season with salt and pepper.