Place the diced bacon into a large stockpot or Dutch oven. Fry over medium-high heat until the bacon is tender-crisp, then remove the bacon slices and place on a paper towel to drain.
Reserve 2 tablespoons of the bacon grease in the pot and drain the rest out.
Place the onion in the bottom of the pot and saute for 5 minutes. Add in the celery, and continue to saute until the onions are translucent and the celery has softened slightly.
Add in the garlic, and saute until browned and fragrant.
Reserve 2-3 tablespoons of the diced bacon for garnishing/topping, then place the rest into the bottom of the pot.
Add in the potatoes, then pour in the clam juice, chicken broth, thyme and bay leaf.
Bring to a low simmer, and cook until the potatoes are tender and almost falling apart.
Remove the bay leaf.
Whisk the cornstarch into the heavy cream, then whisk into the soup to thicken. Let the soup simmer for 2-3 minutes, whisking to ensure that the soup doesn't burn on the bottom.
Stir in the minced and whole clams and stir until they are heated through. Don't let them actually cook or they will get too tough, they are already cooked.
Season to taste with salt and pepper. Prepare the bread bowls by cutting out a circle in the top, scooping out the insides, then fill with the chowder. Serve with the bread you scooped out.
Garnish with the reserved bacon, minced green onion and oyster crackers.