Ingredients :

• Asparagus — Choose the thin ones. Not the thick ones that look like bamboo stalks — those take forever to cook and end up stringy. Thin spears cook in three minutes, remain tender with a slightly resistant core, and have a much more delicate flavor. To prepare them: a quick rinse under cold water, then snap the base by hand. The stalk breaks exactly where the woody part begins. No need to peel.
• Parmigiano-Reggiano — This is the heart of the sauce. Get the real deal — the one with the name engraved on the rind — and grate it yourself. Pre-grated bagged parmesan contains anti-caking agents that prevent the sauce from binding correctly. A 100g piece is more than enough for four people.
• Egg yolk — Just one yolk for four people, whisked with parmesan and cooking water, creates a silky emulsion. The heat from the pasta gently cooks the yolk — there is no raw egg texture in the result. Just pure creaminess.
• Spaghetti — Long, thin shapes coat better in this sauce than short pasta. Avoid penne or rigatoni here; they wouldn’t hold the creamy emulsion as well. For a gluten-free version, rice or corn spaghetti works very well.