Quote:
	
	
		| 
					Originally Posted by J. Fred Muggs  90% sure you added your oil too fast.  start with yolk and salt, add acid, start adding oil by the drop until it starts to emulsify and then add a small stream | 
	
  I usually do it in a food processor or blender, so I can concentrate on adding the oil independently of any stirring.   Also, a lot of recipes ask for more oil than you'll probably need.  Keep an eye on the texture, and stop pouring when it looks like what you want.
ETA: My favorite mayonnaise.  I usually make it in the spring and summer when the artichokes are in season, but I'm making some in the next few weeks before my basil dies back. 
2 egg yolks
3 tablespoons fresh lemon juice
1/3 cup grated parmesan cheese
3 tablespoons chopped fresh basil
2 tablespoons grainy dijon style mustard
1/2 cup olive oil
1 cup vegetable oil 
Salt and pepper to taste
Process egg yolks, Parmesan, basil, mustard and lemon juice in a food processor or blender for thirty seconds. 
With the machine still running, slowly pour olive oil, then vegetable oil in a thin steady stream through the feed tube to make a thick mayonnaise. 
Season to taste.