Dissolve the sourdough starter discard in the warm milk. Add the remaining ingredients and knead the dough.

Let the dough rise for 3 hours. Shape into balls, round them, and place on a baking sheet lined with parchment paper. Flatten each ball with your hands, then let rise in the turned-off oven until doubled in size.

Make small indentations in the dough, brush with oil, and top with rosemary, cherry tomatoes, mashed potatoes, oregano, and salt. Bake at 350°F (180°C) for about 20 minutes.