COMBINE THE VEAL AND 4 CUPS broth in a 5-quart heavy pot over high heat on top of the stove. Cover and bring to a boil. Remove any scum that comes to the top of the pot, then add the remaining 2 cups broth, the onion, celery, carrot, salt, pepper, nutmeg and lemon. Reduce heat to low and let simmer for 1 1/4 hours, or until meat is just tender. Meanwhile, melt the butter in a medium pot over low heat, and whisk in the flour. Cook, stirring, 2 minutes and remove from heat. Set aside until the meat is cooked. When the meat is done, remove it from the liquid, using a slotted spoon. Pick off and discard any vegetables that cling to the veal. Replace the butter-flour mixture over medium-low heat on the stove and strain the cooking liquid into it, whisking vigorously. Discard vegetables in the strainer. Cook, stirring, until mixture thickens, about 3 to 5 minutes. Add cauliflower and continue to cook an additional 15 minutes. Skim off any residue that rises to the surface. When it's time to serve dinner, add the veal to the cauliflower and sauce and heat through. Place sour cream in a mixing bowl, whisk in 1/2 cup of the hot sauce, then add this to the stew. Do not reheat the sauce after adding sour cream. Pour the stew into a serving dish and accompany with rice pilaf or buttered noodles.