For polenta boil 800ml of water. Pour corn flour (polenta) into the water, stirring permanently. Reduce heat to low and cook for 15 minutes stirring occasionally.
Heat olive oil in a skillet to medium-high. Put pork, leek and mushrooms to the skillet and cook about 2 minutes stirring. Add tomato sauce, salt, pepper and cook 2 minutes more.
Preheat oven to 200 C/400 F. Cover rimmed baking sheet with cooking spray and put pork mass into it. Cover with polenta layer and put cheese cubes over polenta.
Bake for 15-20 till polenta crust is golden. Serve warm.