Heat the butter in a 3-quart pot over medium heat. Once melted, add the turkey bacon and sauté until starting to get crispy, about 3 minutes, stirring occasionally. Add the onion, carrot, and celery, and cook until starting to soften, about 5 minutes, stirring occasionally. Add the garlic and thyme and cook 30 seconds, then add the flour and cook 30 seconds more, stirring constantly.
Add the wine, bay leaf, salt, and pepper; turn the heat up to medium-high and cook until the liquid is reduced by 1/2 to 3/4, about 3 to 5 minutes.
Add the potato and fish stock and let it come up to a boil (the veggies should be just barely covered with liquid). Turn the heat down to low, cover the pot, and simmer until the veggies are fork-tender, about 5 to 10 minutes.
Add the milk and whole fish fillets, making sure they are completely submerged in liquid (they will break into smaller pieces while cooking). Cover the pot and cook until the fish is cooked, about 10 minutes; don’t stir until it’s done. (Make sure it doesn’t boil so the milk doesn’t curdle; the fish is done when it is opaque and flakes easily with a fork.)
Taste the chowder and season with additional salt and pepper as desired.