I am just reading an interview with Jörg Meyer in a German newspaper.
He states that the original recipe is:
60 ml Gin
30 ml fresh Lemon juice
20 ml simple syrup
“Handful” of basil (here he emphasises to use the complete plant - leaves and stalks)
Ice
Shaker
… and shake HARD
Then use two sieves to filter out all plant particles.

I only used Diffords recipe so far. Will try the original for sure.