- 1 ounce hazelnuts (2 tablespoons)
- 3/4 pound green beans, trimmed and halved diagonally
- 2 1/4 teaspoons grainy mustard
- 1 1/2 teaspoons balsamic vinegar
- 1/8 teaspoon fine sea salt
- 4 teaspoons extra-virgin olive oil
- 1 tablespoon flaxseed oil
- 1 teaspoon hazelnut oil
- 1/4 cup finely chopped red onion
- Preheat oven to 325°F with rack in middle.
- Toast nuts in a small baking pan until centers are golden, 15 to 20 minutes (cut one open to test for doneness). Cool to warm, then rub off any loose skins in a kitchen towel. Coarsely chop nuts.
- Cook beans in a 6-quart pot of boiling salted water (1 1/2 tablespoons salt for 4 quarts water) until just tender, 4 to 6 minutes. Transfer to an ice bath to stop cooking. Drain and pat dry.
- Whisk together mustard, vinegar, and sea salt in a bowl, then add olive, flaxseed, and hazelnut oils, whisking. Add beans, nuts, and onion and toss well. Season with salt and pepper.
- Beans can be cooked 1 day ahead and chilled (once cool) in a plastic bag lined with paper towels. Dressing can made and chilled up to 5 days ahead.