Heat the olive oil in a large pot or Dutch oven over medium heat. Add the sliced sausage and cook until lightly browned, about 5 minutes. Remove the sausage with a slotted spoon and set it aside, leaving the drippings in the pot.
Add the chopped onion and celery to the pot. Cook until softened, about 5 minutes. Add the minced garlic and cook for 1 minute more until fragrant.
Sprinkle the flour over the vegetables and stir constantly for 1 minute to cook out the raw flour taste. This creates the base for your thick chowder.
Gradually whisk in the chicken broth, ensuring no lumps form. Bring the mixture to a simmer.
Add the diced potatoes, water, thyme, salt, and pepper to the pot. Return the cooked sausage to the pot.
Bring the chowder back to a gentle simmer. Reduce the heat to low, cover the pot, and cook for 15 to 20 minutes, or until the potatoes are tender when pierced with a fork.
Stir in the heavy cream and frozen corn. Cook for another 5 minutes until the corn is heated through and the chowder is hot, but do not let it boil after adding the cream.
Taste the chowder and adjust salt and pepper as needed. Ladle the hearty chowder into bowls and garnish with fresh parsley before serving.
Notes
For a thicker chowder, mash about 1/4 of the potatoes against the side of the pot before adding the cream.
You can substitute smoked sausage with Italian sausage for a different flavor profile.
This recipe makes excellent leftovers; store cooled chowder in an airtight container in the refrigerator for up to 3 days.