For the corn stock

1. Place cobs (snap or cut in half if too big for pot), onion, parsley, thyme, bay leaf, and peppercorns in a stockpot. Add enough water to cover ingredients. Bring mixture to a boil, then reduce heat and maintain a simmer. Cook for 2-3 hours, until the stock has a strong corn flavor.
2. **If not making corn stock, you can infuse some corn flavor into your store-bought stock: Add chicken or vegetable stock to a saucepan. After removing the kernels from the 6 cobs for the chowder, break cobs in half and add to the saucepan. Bring to a boil, then reduce heat to just below a simmer and cook for 10-20 minutes. Remove cobs.
3. Meanwhile, melt butter in a stockpot over medium/medium-low heat. Add corn kernels, onions, jalapeño (if using), ancho chile powder, and season generously with Kosher salt. Cook, stirring occasionally, until onions have softened and corn is tender, about 10 minutes. Add flour and cook for 1 minute, stirring frequently. While stirring, so that the flour incorporates with the liquid, add in corn stock or your infused chicken/vegetable stock. Bring mixture to a simmer, then add sweet potatoes, season with Kosher salt and pepper, and cook until potatoes are tender, about 10 minutes. Add heavy cream and stir to combine. Simmer for at least 10 minutes, although longer is perfectly fine.
4. Using an immersion blender, blend soup to desired consistency. Alternatively, transfer a 1/4 of the mixture to a regular blender and blend until smooth (hold lid of blender firmly so that the steam doesn't pop it off). Return to pot and stir to combine. Blend more of the soup if you want a smooth consistency.
5. Serve immediately, topped with the scallions. Store leftovers in refrigerator and reheat over low heat.