Notes: You can toast the walnuts (step 1) up to 2 days ahead; when cool, wrap airtight and store at room temperature.
3 cups walnut halves (9 oz.)
1/3 cup plus 1 tablespoon walnut oil
2 tablespoons sugar
About 1 teaspoon salt
1/4 cup Champagne vinegar
1/4 cup minced shallots
2 tablespoons Dijon mustard
About 1/4 teaspoon fresh-ground pepper
1 pound butter lettuce, rinsed, crisped, and torn into bite-size pieces
3 cups rinsed and stemmed red seedless grapes, halved
1 cup finely slivered red onion, rinsed and drained
1/4 cup chopped fresh tarragon
How to Make It
In a 10- by 15-inch baking pan, mix walnuts with 1 tablespoon oil, the sugar, and 1/2 teaspoon salt; spread level. Bake in a 350° oven, stirring occasionally, until nuts are golden brown, about 15 minutes. Let cool.
In a large bowl, mix vinegar, shallots, mustard, 1/2 teaspoon salt, and 1/4 teaspoon pepper. Slowly whisk in 1/3 cup oil until vinaigrette is emulsified. Add lettuce, grapes, red onion, tarragon, and sugared walnuts; mix gently to coat, adding more salt and pepper to taste.