- 1 1/4 pounds small new or baby Yukon Gold potatoes
- 1 tablespoon kosher salt plus more
- 2 tablespoons olive oil
- 1 fennel bulb, trimmed, diced
- 2 shallots, finely chopped
- 4 garlic cloves, finely chopped
- 3/4 cup dry white wine
- 1 pound littleneck clams, scrubbed
- 1 pound mussels, scrubbed, debearded
- 1 pound cockles or small Manila clams, scrubbed
- 6-8 razor clams, scrubbed (optional)
- 1 cup (packed) flat-leaf parsley leaves, coarsely chopped, plus whole leaves for garnish
- 1 1/2 tablespoons unsalted butter
- Freshly ground black pepper
- Place potatoes in a medium saucepan. Add cold water to cover by 2″. Add 1 tablespoon salt. Bring to a boil; reduce heat to low and simmer until potatoes are tender, about 15 minutes. Drain; set aside.
- Meanwhile, heat oil in a large pot over medium heat. Add fennel, shallots, and garlic and cook, stirring often, until soft and fragrant, about 5 minutes. Remove pot from heat; add wine. Return pot to heat; increase heat to high, add littleneck clams, cover, and cook for 1 minute. Add mussels, cockles, razor clams (if using), and potatoes. Cover; cook until all shellfish have opened (discard any that do not open), 4-5 minutes longer.
- Using a slotted spoon, transfer shellfish and potatoes to a warm bowl and transfer any remaining vegetables from pot to a blender. Pour liquid from pot into blender, leaving any sediment behind. Add 1 cup parsley and butter to blender; purée on high until sauce is bright green and thickened, about 2 minutes. Season to taste with salt and pepper. Pour over shellfish; stir to coat. Garnish with whole parsley leaves.