Bring water to a boil and then properly salt it. See the instructions in my video for perfect pasta.
Cook pasta per package instructions.
Melt butter over a medium low heat. Sift in flour and mix to thoroughly combine.
Add sea salt and slowly work in milk. Turn heat up to medium high and bring to a simmer. Cook for 2 minutes over a low simmer, reducing heat as needed. The mixture will thicken.
Turn off heat and when mixture stops bubbling, add in cheese.
Add a handful of the cheese, mix in until fully melted, then add more. You can leave the pan on the burner to assist with melting the cheese. Be careful not to burn.
Using a slotted spoon, scoop out cooked pasta, shaking off all excess water. Transfer to cheese mixture and mix to fully coat.
Do not strain or rinse the pasta.
Do until all pasta is mixed into the cheese mixture and serve.