You’ll need two pans of boiling salted water for this dish: a deep one for the pasta, and a shallow one for the egg yolks.
Set a large bowl over the deep pan to act as a lid, and to warm the bowl – put the butter in it to melt. If you’ve somewhere to do so, warm your serving dishes.
While the water is coming to a boil, prepare the asparagus and the egg yolks (once you start cooking, everything must come together quickly). When the salted water is boiling add the pasta and cook per packet instructions.
Cut off and discard the tough bases of the asparagus, and cut the spears into fine julienne strips.
8 spears asparagus
Meanwhile, separate the eggs. Save the whites for another day, and put the yolks individually into little dishes with a splash of cold water in each to keep them lubricated. Take care not to break the membranes.
4 large eggs
When you are pretty much ready to serve, put the tajarin on to boil. It will only take a minute for fresh, two for dried. Thirty seconds before the pasta is done, add the fine strips of asparagus to the same pan of boiling, salted water as the pasta.
260 g tajarin pasta
When both are verging on done but still al dente, drain the pasta and asparagus (reserving a cup of the pasta water) and toss them in the warmed bowl of butter. Add a dash of the pasta water, if it starts to look dry.
160 g butter
Working quickly, poach the egg yolks – slip them gently into the shallow pan of water and let them simmer for just 30 seconds, until the little film of egg white that you couldn’t help but leave clinging to them has in fact turned white. You want to leave the yolks themselves completely raw and oozing – barely warmed.
While they are poaching, serve the pasta on to warmed dishes – divide it between 4 or between 2, as a starter or as a main.
Make a well in the centre of each dish and use a slotted spoon to lift the egg yolks from their poaching bath and into their new nests of tagliolini.
Scatter with grated parmesan and toasted chopped hazelnuts, and serve immediately.