Asparagus with Walnuts and Vinaigrette

Description
Perfect in springtime, asparagus' natural sweetness contrasts beautifully with this tart vinaigrette. ===Ingredients=== 1 pound fresh asparagus, trimmed 1/4 small onion, very finely chopped 2 tablespoons white wine vinegar 1 teaspoon Dijon mustard 1/2 packet sugar substitute 1/2 teaspoon salt 1/4 teaspoon pepper 1/4 cup olive oil 1 pinch salt freshly ground black pepper 4 cups spring salad mix (mesclun) 1/4 cup toasted walnuts, or almonds

Directions
1. Steam asparagus until crisp-tender. Drain, and pat dry with paper towels. Set aside. 2. Combine shallot, vinegar, mustard and sugar substitute, salt and pepper in a mixing bowl. Gradually whisk in oil. 3. Divide lettuce on 4 plates; arrange asparagus on top and drizzle with vinaigrette. Sprinkle with walnuts.