Step 1 In a medium bowl, whisk together the shallot, garlic, mustard and vinegar. Slowly whisk in the watermelon reduction, then whisk in the oil until fully incorporated. Season to taste with salt and pepper. This makes about 1 1/3 cups vinaigrette, more than is needed for the remainder of the recipe; the vinaigrette will keep, covered and refrigerated, up to 1 week.