Brussels Sprouts with Lemon Walnut Vinaigrette

1 pound Brussels sprouts, trimmed and quartered
2 tablespoons walnut oil
1 tablespoon minced shallot
1/4 teaspoon freshly grated lemon zest
1 tablespoon lemon juice
1 teaspoon whole-grain or Dijon mustard
1/4 teaspoon salt
Freshly ground pepper, to taste

Place Brussels sprouts in a steamer basket and steam in a large saucepan over 1 inch of boiling water until tender, 7 to 8 minutes.

Meanwhile, whisk oil, shallot, lemon zest, lemon juice, mustard, salt and pepper in a medium bowl. Add the sprouts to the dressing; toss to coat.