Into a bowl, add the dry yeast powder along with the olive oil, the water, the warm milk and the sugar, mix it all together. Gradually add the wheat flour along with the salt and keep mixing it all together very well. When the dough starts gaining consistency, mix by hand.
Knead the dough for 5 minutes and let it rest for 30 minutes.
Get a piece of dough and round it into a little ball. Flatten and add a mozzarella dice to the center of this dough. Close the dough, and round it again. Repeat this process with all the dough.
Grease a baking tray with a drizzle of oil and place the pizza balls in it.
Brush tomato sauce all over these balls and top with the grated mozzarella, the sausage slices and the oregano.
Bake in a preheated oven at 180°C (356°F) for 30 to 60 minutes. Serve.