• Cut the kernels from the cob and set them aside. Place the cobs in a soup pot and cover with the broth. Bring to a simmer over medium heat and simmer gently for about 30 minutes.
• Discard the corn cobs and strain the broth.
• Return the soup pot to medium heat and heat the butter. Add the onion and sauté, stirring frequently, until limp. Add the flour and continue to cook, stirring, for another 5 minutes.
• Add the broth to the onion mixture, whisking to remove any lumps; bring to a simmer.
• Add the potatoes and corn kernels. Simmer for 20 minutes, until the potatoes are tender.
• Add the diced ham and pepper, and continue to simmer for 5 minutes.
• Add the scallions and season to taste with Tabasco, vinegar, salt and pepper.

Preparation Notes: This soup can be prepared in advance through step 6, then refrigerated or frozen. Return the soup to a simmer before adding the scallions and seasonings.

Serving Suggestions: Make a smooth purée of avocado and squirt it over the soup in a random pattern, or add chunks of avocado at the last moment. Cut corn tortillas into wedges, toast them in a hot oven until crisp, and float them on the soup.