Rinse the salt pork well to remove some of the salt that it contains. Dice the salt pork. Dice the onions and the potatoes. Combine the butter and the salt pork in a heavy-bottomed saucepot. Sweat the salt pork without color to render some of the fat. Add the yellow onion and cook without color until the onions are translucent. Add the clam juice and bring the soup to a simmer, cook for approximately 20 minutes.
Add the diced potatoes. Cook the soup until the potatoes are tender. Adjust seasoning with salt if needed. Cool the soup and refrigerate overnight.
When you are ready to serve the soup, bring the base back to temperature, add the reduced cream and the clams. Bring the soup to a simmer and hold it hot for a few minutes to cook the clams. Taste the soup and adjust the seasoning with more salt if needed. Serve the soup in warmed bowls with oyster crackers on the side. I like to float a small pat of butter in the chowder, and a pinch of freshly chopped chives for color and flavor.
Reprinted with permission by Executive Chef Micheal Cimarusti of Providence restaurant (Los Angeles, CA)