How to Make It
Put the shallots and dill sprigs in a saucepan and top with the salmon. Add the wine and 2 cups of water; bring to a boil. Simmer over very low heat until the salmon is nearly cooked through, 5 minutes; transfer to a plate and let cool slightly. Break the salmon into large flakes and freeze for 5 minutes to cool.
Meanwhile, strain the poaching broth, reserving 3 tablespoons of the broth and 2 tablespoons of the shallots; discard the dill. Chop the shallots and transfer to a large bowl. Add the horseradish and mayonnaise, then whisk in the reserved poaching broth and the oil and season with salt and pepper.
Add the butter beans and escarole to the dressing and toss. Add the salmon and toss gently. Garnish with chopped dill and serve.