Fill a large pot with water and bring to a rolling boil. Stir in just enough salt to make the water as salty as the ocean, and then add the pasta. Stir, return the water to a boil, and cook the pasta, uncovered, until al dente, according to the package instructions.  Drain the pasta and transfer it back to the pot, tossing it with 1 Tbsp of the butter to keep it from sticking. Cover and set aside.

Melt 2 Tbsp of the butter in a medium sauté pan over medium-height heat. Once melted, lower the heat to medium and add the minced garlic and lion’s mane mushrooms, sautéing until the mushrooms are browned, 3-5 minutes. Season with 1/2 tsp of salt. Remove the pan from the heat and set aside.

In a small pot, melt the remaining 4 Tbsp of butter over medium-high. 

Once melted, lower the heat to medium and add the flour, whisking until smooth and continuing to whisk occasionally for two minutes until you smell a nutty aroma. 

Slowly add the milk, whisking continually as you pour until the milk is incorporated and the mixture is smooth.

Lower the heat to medium-low. Add the cheese and use a wooden spoon to stir until the cheese sauce is melted and smooth. The Parmesan will make the sauce salty but taste a bit (blowing first!) to see if it needs more. Season with the remaining salt. 

Pour the sauce over the pasta and mix thoroughly. Stir in the lion’s mane mushrooms, distributing evenly. 

Serve warm, garnished with parsley if desired. 

Store leftovers in a sealed container in the refrigerator for up to 3 days. Reheat in the microwave or on the stovetop with a splash of milk.