Start this recipe by marinating the beef steaks with a good drizzle of extra virgin of olive oil, crushed garlic clove, rosemary and some crushed peppers. Now prepare the sweet potato flan, sauté the sweet potatoes in a knob of butter and a garlic clove, season well. Stir in the 100g of mascarpone cheese and cook slowly until the potatoes turn soft. Mix the egg yolk, salt, pepper and parsley, transfer the potato mixture in a buttered mould and bake for 15 minutes until the mixture sets and takes a nice golden crust. Next, prepare the onion rings. Peel the onion and cut into 5mm thick discs. Push the onion discs with your finger tips to obtain onion rings. Dip the rings into cold milk, and then pass through the flour and deep fry in hot oil until golden and crispy. Combine the remaining mascarpone cheese with the chopped parsley, some chopped rosemary, the crushed pepper and mustard to obtain a creamy pepper sauce. Grill the beef steaks to your liking, serve drizzled with the mascarpone-pepper sauce accompanied with the potato flan, onion rings and asparagus.