Pour 450ml water into a pan. Add a pinch of salt and cover. Bring to the boil. While the water is coming to the boil, finely grate half the chunk of Parmesan. Chop the butter into chunks. Heat your oven to 180°C/Fan 160°C/Gas 4.
When the water is boiling, slowly pour in the polenta, whisking as you add it so the polenta and water blend together smoothly. Put the lid back on the pan, set the heat to medium and simmer for 5 mins.
Line a small ovenproof dish with baking paper. No baking paper? Grease your tin with olive oil. Stir the chopped butter into the polenta. Add half the grated Parmesan. Spoon it into the ovenproof dish. Top with the remaining grated Parmesan. Bake for 30 mins till a crust forms on the top of the polenta.
While the polenta bakes, peel and finely slice the onion. Halve the pepper. Scoop out the seeds and white bits. Slice it into long lenths. Snap the woody ends off the asparagus by bending the spears and they will snap at the right spot. Roughly chop the spears into 3 cm chunks.
Warm a deep frying pan or wok for 1 min. Pour in 1 tbsp olive oil. Add the beef stir-fry strips. Stir fry for 3-5 mins over a high heat till the beef is browned all over. Lift the beef out of the pan and pop on a plate.
Add the onion, pepper and asparagus to the pan. Season with salt and pepper. Stir fry for 5-6 mins till the veg are tender and a little charred. Add the beef back to the pan with any juices from the plate. Stir fry for 2 mins to warm everything through. Pour in the balsamic vinegar and stir fry for 1 min.
Slice the polenta into wedges in the tin and then arrange them on two warm plates. Spoon over the veg. Shave over the remaining Parmesan cheese to serve.