In small, microwaveable bowl, combine vinegar, onion and tarragon.  Microwave on high about 2 minutes or until vinegar is reduced to 2 Tbsp; set aside.

 

Place egg yolks, mustard, salt and pepper in blender; blend on low 3 seconds.  Put butter in microwaveable cup, cover, and microwave on high until melted, about 2 minutes.

 

With blender on low, gradually pour hot butter into yolks in a steady stream; turn off blender.  Add vinegar mixture, olives, and blend just until combined.  Keep warm.

 

Cook Alaska crab on hot grill about 5 minutes.  Serve with Bernaise sauce.