You can - take what you want now, make this the last crop, leave some stems alone for the crown to strengthen. It's not true that you shouldn't crop after July, although you do need to make sure you leave some stems alone towards end August to die back naturally later. I cropped from mine all through August.

The main idea is to leave plenty of leaves, so they send plenty of starch to the roots to feed next spring's crop--the stalks get thin otherwise.

Funny thing is, Tugbrethil, as a cook, I prefer thinner stems - more likely to be cooked when the crumble topping is, lol!

LOL! That would work better if the really thin stalks didn't get stringy, too! That's been one of the main hazards with trying to grow it our climate.

Don't have that trouble here in london, but Moongrower up in Scotland says there's is too tough from mid July onwards - must be the short growing season up there.