Diminutive Japanese turnips are a bittersweet, beautiful, juicy treat. Steaming brings out the best in them. Serve on a platter to accompany poached or grilled whole fish or roasted meat. Or arrange on individual plates for a pristine appetizer or warm salad course. If possible, choose turnips of equal size so they will cook in the same time. If nasturtium flowers can be had, nothing makes a more vivid finish for the bright-white globes on their dark bed.