Add salt, garlic (optional) and pepper to TM bowl. Mill 3 sec/Speed 9.
Scrape down the bowl.
Add egg and 2 teaspoons of vinegar to TM bowl. Combine 30 sec/Speed 6.
Scrape down the bowl. Add butterfly whisk. Reset the Thermomix for 3 min/Speed 4.
With the MC in place slowly add the oil and the remainder of the vinegar alternately over the 3-minute period. Finish adding the last of the liquid 15 seconds before the end of the timer.
Refrigerate until required.
Notes
For the best emulsification, it's best to use room temperature eggs. Adding the oil very slowly at the beginning will also aid in producing a creamy mayonnaise.