Melt butter in a large stockpot over medium heat.
Add in onion, garlic, 4 tablespoons of vinegar, and 1 tablespoon old bay seasoning.
Cook, stirring regularly, for 3-5 minutes, or until onion has softened
Add in pasta, milk, broth, water, and salt.
Bring to a simmer, and simmer for 10 minutes, or until pasta is cooked to your liking. Stir OFTEN to prevent sticking.
Remove pot from heat and stir in the remaining 3 tablespoons of vinegar, half the white cheddar, half the Monterey jack, and half the asiago blend.*
Once melted, gently stir in the crab.
Taste and re-season, if necessary.
Optional baking step: preheat oven to 375 degrees F and grease a baking dish with cooking spray.
Pour in the cooked mac and cheese and top with remaining cheeses.
Top with panko and 1 tablespoon old bay seasoning
Bake, uncovered, in preheated oven for 10 minutes, or until panko is golden brown and the cheeses have melted
Serve with fresh herbs and hot sauce, if desired, and enjoy!