Sprinkle the gelatin over the lemon juice, using the container for the dressing if possible. Let the gelatin soften briefly, then whisk in the egg and microwave on high for about 35 seconds. You want to get the temp to 160 degrees to kill any salmonella in the egg. (I use an instant-read thermometer to make sure it has gotten hot enough, although in reality it's very rare to get sick from a raw egg. It's more for my own peace of mind than out of any real danger that I go through this procedure, but I'd need to heat the liquid anyway to dissolve the gelatin.) Once you've done this a few times you'll know how much time you need for your particular microwave.
If you used the container for the dressing and you have a stick blender, then blend in the vinegar and other ingredients minus the oil. If not, then scrape the egg/lemon juice mixture into whatever container you're using or into your blender container if you don't have a stick blender, add the vinegar/other ingredients as above, and process well. Then slowly pour in the olive oil and blend until completely emulsified; you can tell this has happened when the color becomes lighter and the dressing looks creamy.
This recipe makes a delicious, not-very-strong dressing that will please most tastes. My favorite combo to use with it is: romaine or leaf lettuce, roasted red peppers, thinly-sliced red onion, and homemade croutons. Spinach and pine nuts would also be good (if you can stand to pay for the pine nuts).