Dissolve the brewer’s yeast in a glass of warm water with a pinch of salt. Pile the flour up to form a little “volcano” and, slowly, pour the water with the yeast into the centre. Add a spoonful of olive oil, mix the ingredients together well and knead at length until you have a smooth, elastic, firm dough. Roll it into a ball and leave it to rest for about 2 hours, in a bowl covered with a tea towel, in a warm place.
When the dough has doubled in size, roll it out until it’s roughly 1.5 cm thick, then cut it in half and shape each piece into a disc. Grease the bottom of two, appropriately sized, round baking tins with olive oil and lay the dough in them, using your fingers to form a “crust” all round the edge. Cook the two pizza bases in a preheated oven, at 200 °C, for about 15-20 minutes. When they’re biscuit coloured and crisp around the edge, but still soft in the centre, take them out of the oven and add the topping. Quickly spread an abundant layer of Viallella over the surface, and then sprinkle icing sugar on top as desired. Serve immediately, before it gets cold.