If using canned clams, drain the clams with a strainer over a bowl. Measure the liquid and add bottled clam juice to reach cups.
In a large stock pot or Dutch oven, sauté the bacon until crispy and the fat is rendered out. Remove the bacon to drain on paper towels and strain the bacon fat into a measuring cup. Return the pot to the heat and add back in 2 tablespoons of the bacon fat and the tablespoon of butter.
Add in the leeks, shallot, onion, carrots and celery. Saute until the leeks start to caramelize, stirring frequently, about 7 minutes. Add in the garlic and stir another minute. Add in the white wine and stir until its absorbed. Add in the milk and potatoes and stir. Add in the bay leaves, fresh thyme and clam juice. Bring to a boil, cover the pot, lower heat and simmer for 30 minutes.
Remove the thyme sprigs and bay leaves. Transfer 2-3 cups of the chowder to a blender, making sure there are plenty of potatoes in the mixture, and blend until smooth and thick. Transfer back to the pot and stir well. Add in the chopped clams and the half and half. Cover and keep on low for another 30 minutes. Taste the chowder and season with sea salt and pepper. Ladle into bowls and garnish with bacon, parsley and steamed clams if desired. Serve hot with crusty bread, wine and hot sauce.