Anyway, I planned to use a commercial instant tuna spread as a filling in the first place but couldn't find any in a small supermarket where I stopped by. Given ingredients needed could be all found in the cupboard, I then had second thoughts about making my own filling!
Luckily, not only what I created was so easy to make but it also was edible! Honestly, it was much better than I thought..tasty and surprisingly went along very well with the tart base..:)
The recipe for the dough could be found here.
And what I used for my fillings are the following..
1 canned tuna in oil
3 crab sticks ( Japanese style) ,finely chopped
1/2 - 3/4 cup ( approximately ) real mayo
a quarter of small onion, finely chopped
2 spring onions ( green part only), finely chopped
dried parsley , paparika, cayenne pepper ,curry powder, black pepper and caster sugar to taste
Mix everything together in a mixing bowl ..adjust all seasonings to match your own preferred taste.