Peel and slice the potatoes and the rennets, mince the onion and the leek and put everything in a saucepan.
Add 2 tablespoons oil, put the lid on and let it cook on a low flame for 7-8 minutes. Pour a ladle of warm stock, cover again and let it cook for 10 minutes: then uncover and let it dry up slowly.
Meantime, prepare a cherry tomatoes salad, cut the endive into little strips: add some salt and chive finely cut.
Toast the slices of bread, spread the rennets and potatoes sauce and garnish each toast with a spoon of salad. Serve.
(1) Boil a carrot, an onion, a stem of celery and a little tomato in slightly salted water for half an hour.