To prepare the corn stock, break the corncobs in half. Using a sharp knife, cut the kernels off the cobs; reserve the kernels for the chowder (you will need 3 cups corn kernels). 

Using the side of a spoon or a butter knife, scrape down the sides of the cobs into a deep stockpot to release the "milk" and loosen any bits of corn. Add the cobs to the pot along with the water and onion.

Set the pot over medium-high heat and bring to a boil. Reduce the heat to medium-low and simmer for 20 minutes. Let cool slightly. Strain the stock into a large bowl, pressing on the solids; discard the solids. You will need 4 cups corn stock for the chowder.

To prepare the corn chowder, in a large pot over medium heat, cook the bacon, stirring occasionally, until crisp. Transfer to a plate. 

Pour off all but 1 tablespoon fat from the pot. Place the pot over medium heat, add the onion and fennel and cook, stirring occasionally, until translucent, about 4 minutes. Add the potatoes, reserved corn kernels and corn stock and bring to a boil. Reduce the heat, cover and simmer until the potatoes are tender, about 10 minutes.

Whisk in the potato starch, add the cream and bacon and bring the chowder to a boil. Season to taste with salt and serve.