Cut the trimmed spring greens in half lengthways. Bring a wide, shallow pan of salted water to the boil and add the spring greens. Bring back to the boil and cook briefly, about 1-2 minutes, then drain well.
Mix the crème fraîche in the pan with a sprinkle of sea salt and freshly ground black pepper and bring almost to the boil. Carefully add the spring greens so they don’t overlap too much and reheat gently.
Transfer the greens to a warmed shallow dish and spoon over the crème fraîche. Sprinkle with a little black pepper and serve immediately.