Get a pasta cooker ready for boiling pasta. Fill and add 1 teaspoon salt.

In a double boiler or two saucepans one with water to gently heat the upper pan, heat gently until water begins to simmer and heat the upper pan.  

Place a half stick of butter in the upper pan with egg or egg plus yolk. Immediately begin to stir as butter melts and egg is stirred to creamy consistency. Keep stirring and keep heat low. You don’t want scrambled eggs. You want the butter and eggs to marry into a happy, creamy delight. After the first half stick of butter melts, add the second half and continue to stir making sure the mixture remains a creamy mixture that slowly begins to thicken. This is the part where you are paying attention to your sauce and not being distracted. When it starts to thicken, take it off the heat. Keep stirring. Next, squeeze fresh lemon juice and stir. Salt to your taste. You did great! Now, add your Greek yogurt and whisk it in until it’s a creamy light yellow. Since it has cooled you can set it aside and it will stay very nicely waiting for its curtain call in the next act.

Make sure you have your asparagus ready to plop into the pasta water when the pasta is almost done. I usually peel the tough ends and use the whole stock. If it’s skinny just break it where it easily breaks and save the ends for stock later or toss in the composter. 

Turn on the heat in the pasta cooker. When it’s boiling add your pasta. I place a wooden spoon across the pot in case you get distracted. If it foams up it wont boil over! Cook your pasta until almost done and just before you take it out plop your asparagus into the pot just at the top. Watch it until it turns bright green which happens fast and use tongs to take it out! Run it under cold water immediately to stop the cooking so it will stay bright green. Drain your pasta. 

I like to have a large pasta bowl warmed and ready. Dump the pasta into the serving bowl, place the bright green asparagus on top arranged artistically, or however you like. Pour the sauce over all of it. Place lemon wedges around the sides and add parmesan to your liking!