This bright and bracing salad balances out the rich, heavy flavors of many holiday dishes.
In a small bowl or jar, whisk or shake shallot, vinegar, mustard, and oil until thickened and combined; season with salt and pepper.
In a large bowl, combine spinach and endive; toss with dressing. Serve immediately.
To make this salad ahead of time, refrigerate salad greens and dressing in separate containers until ready to us. Combine and toss with dressing just before serving.