Ingredients

1 tablespoon Dijon mustard

2 teaspoons white-wine vinegar

4 tablespoons olive oil

Coarse salt and ground pepper

1 small red onion, halved and thinly sliced

3 slices white sandwich bread (crusts removed), halved and cut into 1/4-inch-wide sticks

1/2 teaspoon fresh thyme leaves

1 head green-leaf lettuce, washed, dried, and torn into bite-size pieces

2 celery stalks, thinly sliced

Preparation

Preheat oven to 350 degrees. Make dressing: In a large bowl, whisk together mustard, vinegar, and 3 tablespoons oil. Season with salt and pepper. Mix in onion; let stand for 15 minutes to soften.

Meanwhile, make croutons: In a medium bowl, combine remaining tablespoon oil, bread, and thyme. Season with salt and pepper; toss. Arrange in a single layer on a baking sheet; bake until golden, 10 to 15 minutes. (If making ahead, store in an airtight container at room temperature up to 1 day.)

Add lettuce and celery to bowl with dressing; toss. Divide among serving plates, and serve topped with croutons.