In a large pot over medium heat, melt the 3 Tbl butter. Add the onions, celery and garlic and let them cook until the onions are translucent, 3 to 4 minutes.
Add the potato, milk, cream, clam stock, salt, pepper and oyster liquor.
Turn off the heat, and add the shucked oysters. Let the oysters steep in the hot stock until fully cooked and the edges start to curl, 2 to 3 minutes.
For the kelp brown butter garnish, melt 1 cup butter until it starts to foam and the milk solids start browning and produce a nutty aroma.
Toast a sheet of kelp or nori at 375° for 3 to 4 minutes. Blend the browned butter and kelp until the kelp is speckled throughout.
Top soup with browned butter. Serve immediately.
Notes
This recipe was featured on an episode of the PBS series, "Moveable Feast with Relish," available for streaming on GBH Passport. Chef Renee Touponce, a James Beard Award Best Chef Semifinalist, is the executive chef at the Port of Call restaurant in Mystic, Connecticut. She was named Chef of the Year at the Connecticut Restaurant Association’s 2022 CRazies Awards.