Bring a pot of water - with steamer or colander fitted on top - to boil.

In the meantime, peel and trim the asparagus stalks. Steam them for 4-6 minutes until just tender and remove from heat.

While the asparagus is cooking, make the aioli - whisk together the yolk, mustard, and lemon juice until you get a nice and creamy consistency. Slowly add in the olive oil - very slowly! - and whisk rapidly as you see the yolk absorb all that oil and start to emulsify.

Once the mixture is thickened and emulsified, you can be a little more bold about adding in the olive oil as you continue to whisk everything together. Your aioli will be thick and creamy - taste it for seasoning and add salt or lemon juice if needed.

Spoon aioli over the steamed asparagus and enjoy!