• A bit more than 1/2 lb. tagliatelle (or similar long, ribbony pasta)
Bring a large pot of water to a boil.
Meanwhile, bring an inch or two of water to a boil in a small pot. Whisk together the egg yolks, crème fraîche, Parmesan and garlic in a large heatproof bowl that will fit snugly in the pot without making contact with the boiling water (a double boiler, in other words).
Set the bowl in the small pot and whisk the egg mixture constantly, occasionally scraping the sides and removing the bowl from the pot every couple of minutes as you whisk to keep the cooking nice and slow (don't let it bubble). The mixture will look thick and clumpy for a few seconds, then become liquidy, and then, once the cheese has melted, silky smooth. Cook just until the liquidy sauce has thickened slightly (it should thinly coat the back of a spoon), 6 to 8 minutes. Set the bowl aside in a warm place.
Salt the large pot of boiling water generously until it tastes slightly less salty than the sea. If you're confident that the pasta and asparagus will finish cooking at the same time, add them both to the water. If you're a worrywart, cook the asparagus first, scoop it into a colander to drain, then cook the pasta. Cook the asparagus until it is juicy with a slight bite, 3 to 4 minutes; and cook the pasta until it is fully cooked, 3 to 4 minutes.
