Cook the bacon. Heat a large soup pot over medium-high heat, then add the bacon lardons. Cook, stirring occasionally, until the bacon is crispy, about 6-8 minutes. Use a slotted spoon to transfer to a paper towel-lined bowl.
Cook the onion. To the same pot, add 2 Tbsp butter and chopped onion. Cook, stirring occasionally, until softened, another 4-6 minutes. Add 2 cloves chopped garlic, then cook 1 minute more.
Make the roux. Stir in ¼ cup of flour, then whisk until the flour has been fully absorbed into the fat, about 1 minute. Continue whisking, then pour in 4 cups of chicken broth. Bring the mixture to a boil.
Add the remaining ingredients. To the pot, add corn kernels, cubed potatoes, fresh thyme, and a bay leaf. Season with 1½ tsp Kosher salt, ¼ tsp black pepper, and ¼ tsp cayenne (if using). Once simmering, cover the pot and cook for about 20-25 minutes. For a stronger corn flavor, add some of the corn cobs directly to the soup pot.
Purée half the soup (optional!). Remove the thyme, bay leaf, and corn cobs, then carefully transfer half of the soup to a blender and process until very smooth. Return the puréed soup to the pot. Alternatively, you can use an immersion blender to blend about half of the soup. If you want a chunkier soup, simply remove the herbs and corn cobs, then continue to the final step.
Finish, then serve. Add 1 cup heavy cream and most of the crispy bacon to the pan (reserve the rest for serving), then stir well. Taste and adjust seasoning as needed. Serve corn chowder immediately with additional crispy bacon, thinly sliced chives, a pinch of flaky sea salt, and some freshly ground black pepper on top. We recommend baguette for dipping!