This soup is the result of a happy accident. I was planning to roast some sweet potatoes to accompany a pork tenderloin, but found I only had two potatoes. I quartered a few pears to roast alongside, and the result was far better than the original planned dish. The leftovers became this soup. The ham adds a salty balance to the sweet, rich soup. —Rivertree kitchen
Heat the oven to 435 degrees F. Peel the sweet potatoes and cut into 2-inch chunks. Remove stems and cores from the pears (no need to peel them) and cut into large chunks. Peel the onion and cut into fat wedges. Place them all on a large cookie sheet in one layer, drizzle with the olive oil, and sprinkle with salt and pepper. Place in the oven and roast for 15 minutes.
Remove the cookie sheet from the oven (leave the oven on). Dot the pears and veggies with the butter and stir well. Sprinkle with the brown sugar and garlic, put the pan back in the oven, and roast for another 15-20 minutes until everything is quite tender and browned in spots.
Scrape the contents of the cookie sheet into a stockpot. Add 4 cups of the stock. (I pour the stock over the cookie sheet to loosen all those flavorful browned bits, and add that to the pot.) Bring the soup to a boil over high heat, reduce heat to medium-low, and simmer for 5 minutes.
Puree with a stick blender, or in batches in a food processor or blender. Return the soup to the pot, taste and adjust seasoning if necessary. Add more stock if the soup's too thick. Stir in the ham, if you're using it, and reheat the soup. Serve at once.