1 teaspoon Dijon mustard
½ cup walnut oil or olive oil
2 tablespoons minced shallot
1½ pounds green beans, trimmed
²/3 cup walnuts, toasted, coarsely chopped
Remove peel from lemon with vegetable peeler and cut into very fine strips. Cut lemon in half. Squeeze enough juice to measure 2 tablespoons, transfer to small bowl. Whisk in mustard, than oil and shallot. Season with salt and pepper.
Cook green beans in pot of boiling salted water until crisp-tender, 5 to 6 minutes. Drain, pat dry.
Combine beans, walnuts, and lemon peel strands in large bowl. Add dressing : toss to coat. Season salad to taste with salt and pepper and serve. Serve warm on room temperature.