Kosher salt to taste
1 cup mixed shell beans, such as cranberry, fava, lima, flageolets, and/or butter beans
3 tablespoons unsalted butter, softened
1 small onion, finely diced
1 cup fresh corn kernels (from about 1 large ear of corn)
1 cup Chicken Stock, high-quality low-sodium store-bought chicken stock, or water
Black pepper from a mill
1 large shallot, finely diced
Four 6-ounce wild salmon fillets, skin and any pin bones removed
1/2 cup Fish Stock
1/2 cup dry white wine
1 teaspoon freshly squeezed lemon juice
1/3 cup heavy cream
1/2 cup (1 stick) cold unsalted butter, cut into 1/2-inch cubes
3 tablespoons fresh basil (preferably a mix of green and purple basil) cut into chiffonade
- Bring a large pot of salted water to a boil and fill a large bowl halfway with ice water. Add the beans to the boiling water and blanch for 2 to 3 minutes, then drain, transfer to the ice water to stop the cooking and set the color, drain again, and set aside.
- Heat a wide, deep, heavy-bottomed sauté pan over medium heat. Add 2 tablespoons of the softened butter and, when it has melted but not browned, add the onion. Cook until soft and translucent but not browned, 8 to 10 minutes. Add the corn and blanched beans and stir to heat through. Pour in the stock and raise the heat to high. Continue to cook until the liquid has almost completely reduced but enough remains to lightly coat the vegetables, about 5 minutes total. Be careful not to overcook the sauce, as the vegetables may discolor. Season to taste with salt and pepper and set aside, covered, to keep warm.
- Rub the remaining 1 tablespoon softened butter over the bottom of a deep, heavy-bottomed 10-or 12-inch sauté pan. Sprinkle the shallot over the bottom of the pan and set the salmon fillets on top without crowding them. Gently pour the stock and wine over and around the fish to come about two-thirds up their sides. Cover the pain tightly with a lid or aluminum foil, set over medium-high heat, and bring the liquid to a rolling boil, about 3 minutes. Reduce the heat to medium and cook the fish for another minute. Remove the cover and use a fish spatula or regular spatula to carefully remove the fillets from the sauté pan and transfer them to a large plate or platter. (They will be slightly undercooked, but will continue to cook via carryover heat.) Cover loosely with foil. (If you used foil to cover the pan, you can use that to tent the fish.)
- Drain and discard all abut 1/3 cup of the poaching liquid from the pan. Add the lemon juice and a pinch of salt. Place over high heat, bring to a boil, and cook until reduced by half, about 3 minutes. Stir in the cream, bring back to a boil, and continue to boil for 1 minute. Reduce the heat to medium and whisk in the cold butter, a few pieces at a time, incorporating each addition entirely before adding more. Season to taste with salt and pepper and keep warm. Stir in the basil just before serving.
- To serve, drain the succotash in a strainer and divide it evenly among 4 dinner plates. Place the salmon on top and generously spoon over the sauce. Serve immediately.