First of all make the bread dough for the schiacciata.
Sift the flour on a wooden surface and make a well in the centre. Dissolve the yeast in a few tablespoons of warm water and pour it into the well with a few tablespoons of olive oil.
Knead the dough adding a few tablespoons of water at time, until you have an elastic and not sticky dough.
Set aside in a bowl greased with olive oil and leave to rise for about one hour and a half.
It should double its size.
Now knead the dough again with a tablespoon of olive oil, halve it and flatten one half into a rectangular baking pan with high edges, 15 cm wide and 30 cm long, previously generously greased with olive oil. Drizzle half of the grapes on it, press them into the dough and sprinkle generously with sugar. Cover with the remaining dough, flattening it and sealing all around the edges.
Sprinkle with the remaining grapes and sugar, drizzle with some extra virgin olive oil to grease the surface and set aside to raise again for about one hour.
Preheat oven to 190°C and bake the schiacciata for about 40 – 45 minutes, until it is glossy and golden.
Serve warm or cold.