When you live in an area where you can get king crab knuckles at $10 USD a pound, forget about the shrimp! We Alaskans know to buy crab knuckles rather than legs if we don't specifically need huge pieces of crabmeat which legs do provide. However, you are wasting a lot of money on shell weight which is why crab knuckles are preferred -- more crabmeat and a lot less shell which is quite paper-thin. Remove the shells with scissors and pick out all the meat you can. If you don't have any roasted garlic confit paste, check out this link and make ahead of time -- roasted garlic confit paste.
In a large saucepan, bring water to a boil. Add four pinches of sea salt.
Remove shell and cartilage from crab knuckles. Pick out crabmeat and set aside.
In a medium-sized saucepan, melt butter with olive oil to a very gently simmer. Add crabmeat and mirin and very gently simmer for five to ten minutes. Add garlic confit paste and salt and pepper as desired.
Add angel hair pasta to boiling water and cook until al dente. Drain and divide pasta up into individual, pre-warmed pasta plates.
Spoon crab scampi onto pasta, sprinkle with chopped parsley, and serve immediately!
Have guests sprinkle grated Pecorino Romano as desired.
I like to have my king crab scampi piping hot from the beginning to the very end of the dinner. A way to achieve this is to use large butter warmers and keep the king crab scampi nice and warm. I would top my angel hair pasta with a few spoonfuls of the scampi at a time rather than dump it all onto the pasta plate. Another option is to preheat thick-walled bean pots which hold heat very well.