You can make this with a metal whisk but I do not recommend that. Use either a food processor or a blender. I usually use a blender.
1 large egg
1 tablespoon Dijon mustard, or your favorite prepared mustard
1-4 cloves garlic, depending on you enjoyment of garlic. You can chop the garlic if you want or just leave it whole.
1 teaspoon salt
1/4 teaspoon freshly ground black pepper--or ground black or white pepper if you don't have a pepper mill
1/4 cup olive oil
Put the above ingredients in your blender jar and blend well for 1-2 minutes until everything is creamy and there are no garlic chunks visible. Scrape down the sides of the jar so that all the goodness is incorporated.
3 tablespoons balsamic vinegar
1 teaspoon sugar
Blend for a few seconds then add in a very thin stream while the blender runs constantly:
1 cup vegetable or canola oil
After less than a minute you should have a lovely thick very tasty mayonnaise. Scrape down the sides again so everything is together. Remove from the blender jar and store in a covered glass jar in the refrigerator. Use it up in a week, or two at the most.
This is a wonderful sauce on steamed vegetables. It is great on toast with thinly sliced sweet onion and a sprinkle of sauerkraut. It adds a terrific zip to egg salad or tuna salad or potato salad. Especially if you went heavy on the garlic!
If you are on a lower fat eating plan for a few weeks, you might want to share some of this with a friend then make more when you can wholeheartedly indulge again.
You know, I think I will try this on a baked potato soon. No need for butter or sour cream at all!
If you are less adventuresome or prefer a more bland mayonnaise, you can make the same sauce but change the vinegar from balsamic to plain white vinegar, and drop to 1 clove garlic, or none at all. For the mustard, choose a milder mustard. It will still be good mayonnaise. There is nothing like fresh mayonnaise. You know what is in it.
This makes about 1 1/2 cups delicious flavor-filled mayonnaise.