Yes, you can. The two tricks to making mayonnaise are to add the oil slowly and to whisk quickly; but once all of the oil (and at the end the seasoning) has been incorporated, do not keep whisking. Otherwise, you could break your emulsion. This is also one of the reasons why I prefer to hand-whisk mayo vs using a blender or food processor - it is much harder to over-beat and therefore break your emulsion when hand whisking.