Start by boiling a pot of water and cook a couple of organic or well-cleaned potatoes. Once cooked, let them cool and save the cooking water.

While the potatoes are boiling, dissolve the sourdough starter thoroughly in a bowl with milk at room temperature.

After the second rise and once the dough is airy, stretch it out to fill the pan using only your well-oiled hands. Top with tomatoes, pressing them deeply into the dough. Add olives, rosemary, and salt. Bake at 400–450°F (200–230°C) for the first 10 minutes on the bottom rack of the oven. Then move the focaccia to the middle rack and lower the temperature to 350°F (180°C) for 30 minutes. The focaccia will be soft inside and crisp on the outside. Remove from the oven and serve!

Note: Baking times and temperatures may vary depending on your oven. Our oven runs hot, so for the first few minutes, we don't go above 400–450°F (200–230°C). For a more even result, you can also bake at 350°F (180°C) for 35–40 minutes.