The best January dishes bridge the divide between healthful and heavy. They're warming and sustaining, but still full of vegetables and whole grains. This spinach soup does exactly that. Loaded with greens, celery, leeks and herbs, it's got vegetables galore. Some potato puréed into the broth gives it a creaminess without richness. And farro stirred in at the end gives it texture and an earthy depth, making this recipe walk the line between soup and stew.