Dissolve the yeast with salt sugar and 100 g of flour in lukewarm water. Leave a hot down for 15 minutes to rise. Sift the remaining dough in a deep bowl, do well and spills rise yeast and 100 ml olive oil. Stir well with a wooden spoon until a homogeneous mixture. Knead the dough by hand, cover the bowl and leave to rise for about 1 hour depends on the heat in the room. During this time, chop the onion and fry crescents in the remaining olive oil. Spread in a greased pan with olive oil risen disc of dough, put it in a cold oven and turn the oven to 50C degrees. After 15 minutes, take out the tray from the oven and increase the degree of 180C. Spread the onions on Focaccia, optional and sprinkle a little olive oil, return the pan in the oven and bake 20 minutes.