How to Make It
In a large saucepan, combine the ginger, carrot, leek, fennel tops, water, wine and 1 tablespoon of salt and bring to a boil. Cover partially and simmer over low heat for 20 minutes.
Add the shrimp to the broth in the saucepan, cover and remove from the heat. Let stand at room temperature for 20 minutes. Refrigerate overnight.
Mince 2 teaspoons of the grapefruit zest; set aside. Using a sharp knife, peel the grapefruit; be sure to remove all of the bitter white pith. Working over a bowl, cut in between the membranes to release the grapefruit sections.
In a medium bowl, whisk the reserved zest and the grapefruit juice with the olive oil, vegetable oil and sugar. Season with salt and pepper. Add the sliced fennel, toss to coat and let stand at room temperature for 15 minutes.
Remove the shrimp from the cooking broth and pat dry. Arrange the spinach in the center of 6 plates. Using a slotted spoon, remove the fennel from the dressing and mound over the spinach. Add the shrimp and grapefruit sections to the remaining dressing in the bowl, toss and then arrange around the salad. Drizzle with the remaining dressing and serve.