The soup is so simple and easy to make, but tastes fan-tas-tic! Cut the greener part of a few leeks in small chunks (use the white for another dish). Peel and cut a potato that will serve as a binding agent in the soup. Clean 2 handfuls of watercress, soft stems included. Sweat the leek for at least 10 minutes in a little olive oil.I added a sprinkle of lovage seeds aka ajowan (tastes somewhat like thyme). Add the potato, cut in chunks. Submerge all entirely with chickenstock. Cook for 20-30 minutes. Only now, add the watercress. Cook the watercress for no longer than 10-20 seconds!!! Take from the heat and blend. Sieve if necessary. Puff pastry additions; cut some bacon into very small equal strips. Take a sheet of puff pastry (mine was round, so I cut it into a square, which is totally redundant now that I think about it again). Paint the surface with some beaten egg. Sprinkle the bacon on it, then generous pecorino. Roll or fold the pastry into a sausage. Cut in small slices, paint again with the beaten egg and put in the oven at 200°C/400°F as long as necessary. You could certainly serve these as a snack on their own! Totally delicious soup. The more watercress you put in the darker green it gets.