Focaccia sandwich with ham and mozzarella

In a large bowl, combine the all-purpose flour, salt, and sugar. Add the dry yeast to the lukewarm water and let it stand for five minutes until small bubbles appear on the surface. Pour the yeast water into the flour, add one tablespoon of olive oil, and mix until you get a very sticky, soft dough. Cover the bowl tightly with plastic wrap and place it in the refrigerator for 24 hours. During this time, the dough will double or triple in size and be full of bubbles.

Prepare a baking tray approximately 40x30 cm and grease it thoroughly with 2 tablespoons of olive oil. Place the risen dough onto the tray and gently spread it with your fingers to the edges to form an even layer. Cover again with plastic wrap and let it proof for another 2-3 hours at room temperature.

When the focaccia has perfectly risen, preheat the oven to 220°C. Drizzle the top of the dough with the remaining olive oil. Using oiled fingers, press indentations into the dough, then sprinkle with a little coarse salt. Bake until golden brown in the hot oven for about 25-30 minutes. The finished focaccia should be bubbly, crispy on the outside, and soft on the inside.