Roll out the dough & prepare the bottom of the pie in a baking dish with baking paper underneath.
Boil the potatoes in some water with the fish cube in it. Cook for 10 minutes or until the potatoes are halfway cooked through.
In a frying pan, heat up the oil.
Add the onions & garlic. Season them with salt & pepper. Cook them for 5 minutes over medium heat, stirring occasionally.
In a large bowl, mix the potatoes, onions & garlic, drained tuna, parsley, olives, capers & anchovies.
Cook the bottom of the dough until lightly golden brown.
Take the bottom of the dough out of the oven, add the mixture to it & close the pie with the remaining dough. Up to you if you do the top dough whole, strips like I did or get creative. Cook in the oven for 25 to 30 minutes