Cook white potatoes until tender, cut into quarters and cool completely, preferably overnight in the fridge
Add potatoes to a mixing bowl with butter beans, cannellini beans, basil, dill and half the chives, capers, and shallots
Add a splash of extra virgin olive oil and season with sea salt and black pepper, then toss
Make the dressing by whisking together yoghurt, horseradish, lemon zest and lemon juice
Pour dressing over the salad and toss again
Divide between bowls and top with flaked trout
Squeeze lemon juice over each bowl, crack black pepper and garnish with remaining chives
