Place the bacon pieces in a cold large Dutch oven. Set over medium heat and cook, stirring occasionally, until the fat is fully rendered and the bacon is crispy and golden, about 8 to 10 minutes. Use a slotted spoon to transfer the bacon to a paper-towel-lined plate, leaving all the drippings in the pot.

If there is more than 2 tablespoons of bacon fat in the pot, pour off the excess, leaving about 2 tablespoons behind for maximum flavor.

Add the diced onion and celery to the pot with the bacon fat. Cook over medium heat, stirring occasionally, until softened and translucent, about 5 minutes. Add the minced garlic and cook for 1 minute more until fragrant.

Add the 4 tablespoons of butter to the pot and let it melt into the aromatics, stirring to combine.

Sprinkle the flour over the onion-butter mixture and stir constantly for 1 to 2 minutes, cooking the flour until it smells slightly nutty and there are no white streaks remaining. This roux is what gives the chowder its signature thick, velvety body.

Slowly pour in the bottled clam juice and the reserved juice from the canned clams, whisking constantly to prevent lumps. Add the chicken broth and whisk until completely smooth.

Add the diced Yukon Gold potatoes, thyme, bay leaf, salt, and black pepper to the pot. Bring to a gentle boil over medium-high heat, then reduce heat to medium-low. Simmer uncovered, stirring occasionally, until the potatoes are just fork-tender, about 12 to 15 minutes.

Remove and discard the bay leaf.

Reduce heat to low. Pour in the heavy cream and stir to combine. Add the drained chopped clams and stir gently to incorporate. Heat the chowder over low heat until it is steaming hot throughout, about 3 to 5 minutes. Do not allow the chowder to boil at this point — boiling cream can cause it to separate and will toughen the clams.

Taste and adjust seasoning with additional salt and black pepper as needed. If the chowder is too thick, thin with a splash of clam juice or whole milk. If it is too thin, mash a few potato pieces against the side of the pot to release their starch.

Ladle the hot chowder into warmed bowls. Top each serving with the reserved crispy bacon pieces, a scatter of fresh chives, a grind of black pepper, and oyster crackers on the side. Serve immediately.