Place egg and lemon juice in blender. If they're not already at room temp, wait 30 - 60 mins until they reach room temp. Add dry mustard, salt and ¼ cup of the olive oil. Blend until well mixed, about 20 - 30 secs. Incorporate remaining 1 cup olive oil by very slowly drizzling into the mixture, not to break the emulsion. It takes about 3 mins. Be patient.A Few Tips:All ingredients must all be at room temp. Take your time, and then go slower than that. For homemade mayo expiration date: look at the expiration date on the eggs, then add about a week. “Light tasting” olive oil will result in a more traditional mayonnaise taste rather than darker “extra virgin” olive oil.If something goes wrong and the mayo comes out a consistency more like salad dressing and less like mayo, chill for a few hours, and then stir vigorously. It will be less creamy than the typical mayo, but not wasted!  (Recipe♦484)