Dissolve yeast in 1⁄2 l very cold water. Mix 600 g flour, 1 1⁄2 tbsp salt and yeast water with a wooden spoon to a soft dough. In a very large bowl (at least twice the size of the dough), seal it airtight.
Allow the dough to rise for about 4 hours at room temperature or at least 12 hours in the refrigerator.
Cut baking paper into 12 pieces of approx. 20 x 20 cm. Line each recess of a muffin tray (12 recesses) with a piece of baking paper. Preheat oven (electric cooker: 200 °C/circulating air: 175 °C/gas: see
Grate Gouda finely, cut mozzarella into small pieces, dice tomatoes roughly. Knead cheese and tomatoes into the dough. Form 12 balls from the dough on a lightly floured work surface and place them in the recesses of the muffin tray.
Bake in a hot oven for about 40 minutes.