Peel the asparagus, if you also use green asparagus, only peel the lower third there. Bring 1/2 liter of water with sugar, salt and butter to the boil. Add the white asparagus to the water and cook for about 15 minutes. Do not add green asparagus to the water until 5 minutes after the white one.
Peel and finely dice the onion and fry in olive oil until translucent. Add the mascarpone and 300 ml asparagus stock, heat up and reduce a little. Add sparkling wine and fresh tarragon leaves to the sauce and season with salt and pepper.
Tagliatelle go well with this. And for meat lovers, fried pork medallions wrapped in bacon.