Bring the milk and bay leaf to simmering point in a large, heavy-based saucepan. Add the fish and poach for six minutes. Remove from the pan with a slotted spoon.
Heat the oil in a heavy-based frying pan and fry the bacon lardons until crispy. Add the onion and garlic and fry for a further five minutes. Pour in the wine and cook until the volume of liquid has reduced by half.
Add the lemon juice and zest, crème fraîche, butter beans and peas. Cook for a further five minutes, stirring regularly.
To serve, divide the beans and peas between four bowls. Place the fish on top and garnish with parsley.