Wash and cook the potatoes, then peel and leave to steam. Meanwhile, mix the yeast with a pinch of sugar, 3 tbsp lukewarm water and 2 tbsp flour and leave to rise in a warm place. Press the potatoes through a ricer and mix with the flour, yeast mixture, 2 tbsp oil, salt and water to form a smooth dough. Cover the dough and leave to rise in a warm place for 1 hour.
When the dough has risen by 1/3, knead again briefly, roll out, place on a lightly oiled 40 x 25 cm baking tray and leave to rise for a further 30 minutes. Wash and halve the cherry tomatoes, pluck the rosemary needles and tear the goat's cheese into small pieces. Mix everything with the remaining oil and season with salt and pepper. Spread the mixture over the dough.
Bake in the preheated Monolith over an indirect heat at 240 degrees, then sprinkle with fleur de sel.
