Peel and chop the vegetable onion. Heat the oil in a large pot and sauté the onion in it. Add the rice and steam it while stirring until it becomes glassy. Deglaze with white wine and boil down while stirring. Add stock in portions and simmer at low heat, stirring frequently.
Wash the asparagus, peel the lower third and cut off the woody ends. Cut asparagus diagonally into thin slices. Peel prawns, except for the tail fin, and remove the intestines. Wash shrimps and dab dry.
After 20-25 minutes the rice should be ready: soft but with a firm core. Stir Parmesan and 30 g butter into the risotto and season with freshly ground pepper. Heat 20 g butter in a frying pan and sauté the asparagus slices for 4-5 minutes while turning. Remove from the pan. Add the remaining 20 g butter to the hot pan. Add the prawns and fry them for 3-4 minutes, turning.
Add asparagus again, heat everything briefly and season with salt and pepper. Arrange risotto in deep plates or bowls and spread asparagus and prawns with the brown butter on top. Serve garnished with lemon and dill.