Basil- How much can I pick at once?

[anakiwa]

Fairly new gardner here-
I have 6 healthy basil plants in the garden. I'd like to maximize the amount of pesto that goes into the freezer over the course of the rest of the summer. How aggressively can I pick the leaves off the basil plants without damaging the plant and jeopardizing future harvests?
Thanks

[Trentt]

I pick up to half of each major stalk, leaving enough leaves to produce energy for the plant. I do this not only because I like basil, but also to prevent the flower spikes from forming.