How to keep a rolled cabbage leaf (stalk leaf not the outer leaf) in place? I am growing white cabbages and have an idea to use the stalk leaves (not the outer leaves of the cabbage) in the same way as fried zucchini/courgette flowers.

I want to roll the (raw) leaves (including stem) to form a tube and stuff with anchovy and mozzarella, dip into a batter and shallow fry.

However, I need a way to keep the leaf rolled up (and perhaps even sealed at the end).

Note that the leaves from the stalk of the plant are very different to the leaves which make up the cabbage itself.  The stalk leaves are not stiff and easily roll to form a tube/cone shape without boiling.

Here is a top view of a cabbage growing.  The cabbage heart in the centre will continue to grow and form the final cabbage which is sold to the public.  The stalk leaves of the plant which surround the cabbage heart are discarded when the cabbage is harvested.  I want to use the stalk leaves (and of course the eventual cabbage proper).  In the picture, the stalk leaves are larger than mine and so will be tougher and not as flexible (but will still be pliable compared to the leaves of the cabbage itself).  I plan to use my leaves when they are smaller and easily roll up (but needs something to keep in the rolled shape, preferably edible).

I would prefer an edible solution, so toothpicks/skewers are a last resort.

Ideas


Slice an onion into rings and use a ring or two to keep the leaf rolled in place.  The open end may stay sealed by folding the end over itself with an onion ring holding in place.
Sacrifice a stalk leaf and cut into long, thin strips (discarding the stalk/stem) and use that as string (inspired by using shredded leek). Update: Tried using strips of a leaf, but they break when tying.
Correct me if I'm wrong but you want to make a Spring roll but with cabbage leaf instead of rice wrapper? 
If yes then what you want to make is cabbage roll. 
And it's almost impossible to make with raw leaves. They are to bristle and cook too long to let what's inside cook accordingly. As in it will be overcooked before stuffing will be done. Or if you put ready stuffing it will get soggy. 

What you can do is to boil the cabbage whole and peel leaves that are soft and tender. Then you cut the steam to flatten it (so you cut horizontally).
After that it should be enough to roll stuffing in it and seal it. 

Edible "thread" that you could use is leek cut in length and steamed a little bit so it's softer but still springy.