This is from Nourishing Traditions. I haven't tried it yet.
Makes 1 1/2 cups
1 whole egg, room temperature
1 egg yolk, room temperature
1 tsp Dijon-type mustard
1 1/2 tbsp whey, optional
3/4 - 1 cup extra virgin olive oil or expeller-pressed sunflower oil or a combination
generous pinch sea salt
In your food processor, place egg, egg yolk, mustard, salt and lemon juice and optional whey. Process until well blended, about 30 seconds. Using the attachment that allows you to add liquids drop by drop, add oil with the motor running. Taste and check seasoning. You may want to add more salt and lemon juice. If you have added whey, let the mayo sit at room temperature, well covered, for 7 hours before refrigerating. With whey added mayo will keep for several months and will become firmer with time. Without whey, mayo will keep for about 2 weeks.