For the dough: In a mixing bowl combine flour, yeast, sugar, and salt. Mix 1 minute. Next add water and half of the beaten egg. Mix. Add butter and mix with your hands until combined. Knead by hand until smooth and elastic, about 10 minutes.
Cover the dough and let rise in a warm place for about 30 minutes. After that, punch the dough down and make 8 round balls and allow them to rise for 10 minutes .
Now take out each ball and roll out with a rolling pin until you get a thin disk (diameter 3 inch, thickness 1/4 inch).
For the filling: In a pan heat 1/2 tablespoon of olive oil over medium high heat add garlic and mix. Next add onion, salmon, and mashed potatoes. Mix until onion is softened and everything is heated through. Add pepper and salt. Mix well.
Now place a tablespoon full of filling mixture in the middle of each dough disk and gather the dough up around the filling. Pinch the seam shut. Flatten the dough lightly and dip the dough balls in the remaining 1/2 of the beaten egg and roll them in bread crumbs. Now cover the dough balls and leave to rise about 30 minutes.
Next deep fry them in hot oil (over medium heat), until they are golden brown . Remove them from the oil onto absorbent paper to drain for a minute or two. Then serve hot with tomato sauce or your favourite dipping sauce.