While blanching the spinach, add 1 tsp of sugar because that will retain the green colour in spinach.
Add potatoes lesser than spinach.
Do not add more besan flour otherwise it will make the kebab hard.
The kebab consistency should be soft.
Wet your palms with water because the kebab will be little sticky, so it will be easy to make a shape.
I would say, if you want to make a kebab immediately just directly put them in a pan to shallow fry them because the shape might break if you arrange in plate.
You could also store the in a freezer for 1 week.