Have all your ingredients on hand. This process should take no more that 2 mins, any longer and your mayo could split.
Add egg yolk, Dijon, lemon juice & verjuice to Thermomix Bowl. Set speed to 4. After a few seconds SLOWLY pour half the oil onto the Thermomix lid.
Remove measuring cup (blade is still running at speed 4) add the remaining oil a little faster but not all at once. Add salt and pepper and tobasco sauce.
Stop the Thermomix. Check seasoning and adjust acidity and salt.