The soy-free mayonnaise found in the store can be pretty expensive so I set out to make a homemade equivalent.
1 egg yolk (make sure to check date stamped on cartoon to make sure you are using the most fresh eggs available)
1 Tbs white distilled vinegar
0.5 tsp of salt
0.25 tsp of dried mustard powder
3/4 cup oil (preferably canola or safflower)
Mix the egg yolk, vinegar, salt and mustard powder together in a circular glass container. I've found that containers with steep sides (IE 90 degrees) work much better for the later stages of prep. then do those that have more slanting sides (IE bowls). In order to achieve the mayonnaise emulsion, the oil needs to be added very slowly in the beginning to the egg yolk mixture using a whisk. If the oil is added too quickly than the you will end up with a soupy mess instead of the desired emulsion. To do this you can use a tablespoon to add a couple of drops at a time. Once you have added about half the oil you can start adding oil more quickly. Since you are adding fresh egg yolk the mayonnaise should be used within 3-4 days.
* it should be noted that lemon juice can be added instead of vinegar for those who don't like vinegar. If you are using wet mustard, try using a scant teaspoon instead of the dry measurement.