Add the corn in the husk onto a sheet tray and back in the oven at 425° for about 25 minutes. In a large hot pot on high heat, render the bacon fat and cook the bacon until it becomes crispy.
Once it is cooked, remove the bacon from the pan, turn down the heat to medium, and add in the onions, celery, peppers, and garlic and sweat over low heat for 10-15 minutes.
Deglaze with the cream sherry and cook until it becomes absorbed, and only a small amount remains. The technical term for this is au sec, which means almost gone.
Now, remove the corn from the oven and cool slightly before shucking and trim the kernels off of the cob and add them to the pot with sautéed vegetables along with the potatoes.
Pour in the stock, turn the heat to high, and bring the soup to a boil. In a small bowl whisk together the cornstarch and water and then whisk the slurry into the soup until it becomes very thick.