Mix all the ingredients thoroughly in a bowl until smooth, using a whisk or an electric hand mixer, and season with salt and pepper. If desired, transfer the cream to a piping bag.
Fry the sourdough bread in butter in a frying pan until it turns golden brown.
Cut the cucumber lengthways, scrape out the seeds with a teaspoon, and then cut the cucumber into rough chunks. Toss the cucumber pieces with a little salt, oil and lemon juice and leave to marinate whilst the chives are finely chopped, the lovage is chopped, and the radishes are rinsed and cut into long, thick sticks. Mix everything together.
Spread the smoked cheese cream generously over the toasted bread slices, then top with the salad of cucumber, radishes and herbs.
Finally, garnish the dish with plenty of fresh dill sprigs and a sprinkling of grated lemon zest for extra freshness and flavour.
