After scrubbing the clams under cold water, discard any that are open and don't close to the touch.
Add clams to a large pot (i.e., Dutch oven) with 1 cup of water. Cover and bring to boil and cook for 7 minutes. Carefully remove the lid. If the majority of the clams have not opened up, place the lid back on the pot and continue steaming for another 2 minutes.
Remove the clams from the pot with tongs onto a cutting board.
Line a sieve (or colander) with cheesecloth and place over a large measuring cup. Strain the clam broth through the cheesecloth into the measuring cup. Add additional water to the measuring cup until you have a total of 4 cups.
Once the clams are cool enough to handle, use a small knife, or your fingers, to remove the meat from the clams and roughly chop. IMPORTANT: Discard any clams that did not open during the steaming process.
Meanwhile, heat the oil over medium-high heat in a large pot. Add the cut bacon and cook until crisp, about 5 to 6 minutes.
Add the onion and cook until soft and translucent, about 5 minutes.
Add the salt, pepper, bundled thyme, bay leaves and stir to combine. Add in the potatoes and stir again.
Add the reserved clam juice, turn the heat to high, and bring to a boil. Reduce the heat and simmer until the potatoes are tender, about 15 to 20 minutes.
Add the cream and milk and cook for a few minutes until heated (don't bring to a boil). Add the clams.
Make a corn starch slurry by mixing together in a small bowl 3 tbsp corn starch with ¼ cup of cold water.
Add the slurry to the chowder and stir until slightly thickened. If desired, smash a few of the tender potato cubes against the side of the pot for additional thickening and texture.
If desired, add a few splashes of hot sauce and Sherry. Taste and add more salt, if necessary.
Serve warm in bowls and garnish with chopped parsley and oyster crackers, if desired.