Finely dice the dried tomatoes and onion. Press 1 clove of garlic through a press. Heat 50 g butter. Sauté tomatoes, onions and garlic until translucent. Boil vegetable stock and milk with salt. Stir in polenta semolina and let it swell at low temperature for 20-25 minutes. Fold in butter- tomato mixture and 100 g Parmesan. Brush a shallow work bowl (30×25 cm) with oil. Pour the hot polenta into it, spread it smoothly and let it cool down.
Cut the polenta into 9 squares (A 8×8 cm). Cut 3 squares in half crosswise, place the remaining squares in an ovenproof, lightly buttered gratin dish.
Peel the asparagus spears, the green ones only at the lower third, cut the asparagus ends into small pieces. Cut asparagus diagonally into 2 cm pieces. Cut olives into narrow wedges. Press remaining garlic through a press. Heat oil in a large frying pan. Roast asparagus spears with olives and garlic for 3-4 min, turning. Season with salt and pepper, cool. Drain mozzarella, cut into small cubes and mix with cooled asparagus spears.
4. divide the asparagus mixture evenly among the polenta squares and top each with 1 polenta triangle. Sprinkle remaining Parmesan over triangles and top with remaining butter in flakes.
5. bake the polenta in the heated oven at 200 degrees Celsius (gas 3, convection oven 15-20 min. at 180 degrees Celsius ) on a high heat.