Put the flour in a bowl and press a depression in the middle. Crumble yeast into it. Pour in about 5 tablespoons of lukewarm water. Mix with some flour to a pre-dough. Cover and leave to rise in a warm place for about 15 minutes.
In the meantime, grate the parmesan finely. Crumble the gorgonzola. Mix both cheeses. Add 1/4 l lukewarm water and 4 tablespoons of oil to the pre-dough. Knead everything to a smooth dough. Cover and leave to rise for another 15 minutes.
In the meantime peel and wash the potatoes and cut them into thin slices. Peel garlic and cut into thin slices. Grease a baking tray. Knead the dough again, roll out on a floured work surface and place on the baking tray.
Spread the cheese and potato slices on the dough. Sprinkle garlic on top. Cover with sage leaves. Sprinkle with remaining oil. Bake the pizza in the preheated oven (electric cooker: 225 ° C / gas: level 4) for about 40 minutes.