In a small bowl combine shallots with the vinegar and sherry; let stand at least 20 minutes. Meanwhile, zest 1 of the oranges, avoiding the white pith. Finely chop zest and add to the shallots. Squeeze 1/3 cup juice from zested orange and add to the bowl. Slowly whisk in the olive oil and season with salt and pepper; set aside.

 

Cut asparagus spears in half or in fourths and cook in boiling salted water for 4 to 5 minutes until crisp-tender; drain well and remove from pan to cool. Toss the vinaigrette with the cooled asparagus.

 

Cut the ends of the remaining oranges and peel them by cutting down the fruit vertically, following the contours of the fruit. Slice the peeled orange horizontally into 1/2 inch thick slices. Arrange the orange slices and asparagus spears on salad plates and season to taste with additional salt and pepper. Top each serving with 1 Tbsp toasted walnuts.