First off you need to select your ingredients. You need pasta, mushrooms, cream (+ milk), white wine and egg yolks.
This ingredient is the easiest one, just buy some penne or fettuccine from the grocery store and cook it with two table spoons of salt at very high heat. The water needs to boil hard before adding the pasta. Continue to mix the pasta while cooking it. Do not overcook, it should be "al dente". Not too hard, not too soft. Just right. Make sure that your sauce is ready when your pasta is ready, because you need to mix the pasta together with the sauce.
I like to use brown button mushrooms, because it gives a brownish color to your sauce. Just chop them how you like it. I mostly chop them in thick slices, so that it gives off its flavor to the sauce. Then you take a baking pan, add some butter and sautee them at the highest possible heat. You can season the mushrooms with some oregano/basil/thyme/pepper.
3) White Wine
Then add some white wine to cool the mushrooms down. Let the wine evaporate and then you add the cream.
The cream is one of the more difficult parts of the cooking process, because there are different forms of cream. First off, always use heavy cream, meaning cream with a high fat content above 30%. Otherwise your sauce will separate.
You have the following cream products:
- Crème fraîche
- Sour Cream
Cream (heavy cream) is the most basic one, it is liquid and has a 35% fat content. The French call it: crème fraîche liquide. It is entirely possible to use heavy cream in your mushroom sauce. Just add the cream to the mushrooms, cook it for a bit, add salt and there you have it.
Crème fraîche on the other hand is going a step further. This is cream that has been made sour by adding bacterial culture. The pH of crème fraîche is about 4.5 which is more sour than heavy cream, which has a pH of 6.6. In France, they call this fermented version: crème fraîche épaisse. Meaning, the thick version of cream. So if you want to a have a bit of freshness in your sauce, you can use crème fraîche. The end result will be a bit more sour.
Sour cream is the same as crème fraîche, with two differences: less fat and more sourness. Sour cream has a fat content of 10% in Belgium and 16% in France. In France they call this: crème aigre. I would not advise you to use sour cream in hot sauces, but you can add this in the last two minutes of your sauce, just at the end to get it more sour to your taste. Normally you use sour cream to make cold dipping sauces. For example: 225 g mayonnaise + 200 ml sour cream + parsley + mustard + onions = great dipping sauce.
For all of these creams above, you just need to add those creams into the mushroom mix and let it cook at a low heat. Add milk to make it more liquid. Do not overcook the cream, otherwise you will get into trouble: separation of the sauce, lumps of protein will emerge. The duration of cooking will determine your sauce texture. I like to have a more liquid texture rather than a thick texture, because it will be too heavy. If you do get lumps (curdling), then you need to remove the sauce from the heat and whisk it firmly to break the protein lumps. Also adding some flour to the sour cream mixture helps because the flour coats the proteins and stops them from collecting together. Remember, sour cream doesn't like heat.
If it's too light in texture, you can add some butter to it. If it's too thick in texture, you can add some milk or cream to it.
5) Egg Yolks
The key ingredient and probably the most difficult one to do right is egg yolk and acts like a liaison for the sauce. The egg yolk(s) can be added to the sauce or they can be added to the cooked pasta. Just make sure you don't overcook the egg yolk. Egg yolk begins to coagulate at 65 °C - 70 °C, while egg white coagulates a 63 °C - 65 °C. So make sure to remove all egg white from your egg to get the best result. Also make sure your paste isn't hotter than 70 °C. Otherwise you will have pieces of cooked egg yolk in it. You will get scrambled egg pasta...
If you decide to add the egg yolk to the sauce, make sure the sauce isn't blazing hot. First mix the egg yolk with some cream to get a liquid egg yolk/cream mixture. This will reduce the risk that the eggs will overcook when adding them to the hot cream sauce. Add the egg/cream mixture when the sauce has cooled down a bit (preferably to 65 °C), otherwise you risk cooking the eggs and you will have tiny pieces of egg in the sauce.
If you decide to add the egg yolk to the pasta, make sure your pasta is wet and at the right temperature. Dry pasta doesn't mix too well with the egg yolk. Also, don't add the egg yolk immediately after you cooked and strained the pasta as you will cook the egg yolk. Just leave the pasta on a plate or bowl for a few minutes and then mix the egg yolk in it. Then immediately add the (not blazing hot) mushroom cream sauce to it.
=> The end result will be a delicious pasta with mushroom cream sauce.
I have some issues with the end result. First off the sauce was too thick. Next time I'm going to add more milk to it, I want the sauce to be a bit liquid. Second, the sauce was a bit too sour to my taste, it would be better to mix it with some heavy cream to get the pH a bit higher. Third, the wine evaporated immediately, maybe I should add more wine to it and lower the heat more. Next time I will also add sour cream with some flour to prevent the curdling. The egg yolk addition went pretty smooth. It was edible, but there is room for perfection.