Boil or steam crab legs and then shell. Place meat in a bowl and set aside.
Fully fry (or bake) bacon and roughly chop then set aside.
In a sauce pan, melt 2 tbs butter and add flour over medium heat.
Cook butter and flour mixture for approximately 2 minutes.
Stir in milk, bay leaf, nutmeg and ground mustard. Cook for approximately 6-8 minutes until the mixture starts to thicken. You may need to raise the temperature, being careful not to scorch the milk.
Once the mixture has thicken enough to coat the back of a spoon, lower the temperature and remove the bay leaf.
Add gouda and cheddar cheese and a tablespoon of butter. Stir until cheese is melted.
Add crab meat and bacon and salt and pepper to taste.
Cook pasta according to packaging, drain and stir into cheese mixture.
Put mac and cheese in an oven safe casserole dish and cover with foil.
Bake at 350 degrees for approximately 20-30 minutes, removing the foil halfway through the baking process.
Notes
For this mac and cheese, you can substitute imitation crab meat for crab legs.