1. Cut celery into 3-inch pieces, then slice each piece lengthwise into 1/8-inch-thick strips. Halve each endive lengthwise, cut out core, and slice each half lengthwise into 1/8-inch-thick strips.

2. Whisk together blue cheese, vinegar, 1/8 teaspoon salt, and pepper in a large bowl. Add oil in a slow, steady stream, whisking until emulsified.

3. Toss celery and endive with dressing; season with salt and pepper. Refrigerate until ready to serve. Garnish with celery leaves and blue cheese.