In a large pot or Dutch oven over medium heat, cook the chopped bacon until crisp. Remove the bacon with a slotted spoon and set aside, leaving about 1 tablespoon of fat in the pot.

Add the butter, onion, celery, and carrots to the pot. Cook for 5 to 6 minutes, stirring occasionally, until the vegetables begin to soften.

Stir in the garlic and cook for 30 seconds until fragrant.

Add the corn, potatoes, broth, salt, pepper, thyme, and bay leaf. Bring to a boil, then reduce the heat to a simmer. Cover and cook for 15 to 20 minutes, or until the potatoes are tender.

In a small bowl, whisk together the flour and water until smooth to make a slurry.

Stir the milk, heavy cream, and flour slurry into the pot. Simmer gently for 5 to 7 minutes, stirring often, until the chowder thickens slightly.

For a creamier texture, use an immersion blender to briefly blend part of the chowder, or transfer 1 to 2 cups to a blender and return it to the pot.

Remove the bay leaf. Taste and adjust seasoning with additional salt and pepper if needed.

Ladle the chowder into bowls and top with the reserved bacon and fresh parsley or chives before serving.