Drain half of the tomato sauce from the sardines and place the other half with the sardines in a medium saucepan. Then add the onions and curry powder and let it simmer for 10-15 minutes, or until almost all the liquid has evaporated. Add the parsley, stir, and simmer for about 2 more minutes. Set aside and let it cool.
In a large bowl, mix the warm water and yeast. Set aside for 5 minutes while the yeast activates.
Using a stand mixer (or by hand), mix the flour, sugar, and salt, then add the butter, and mix well until the ingredients are fully incorporated.
Add the yeast mixture to the flour mixture and mix for about a minute. Turn the dough out onto a lightly floured surface, and knead it just until all the flour is incorporated and the dough is smooth.
Cover and let it sit for 30-45 minutes or until it rises.
Divide the dough into pieces of 1-2 ounces each. You should have 25-35 pieces, depending on the weight.
On a lightly floured work surface, roll out each piece of dough with a rolling pin until 1-2" wide and 3-4" long.
Then place a teaspoon of the fish mixture at one end and roll it up. Repeat the process until all the filling and dough have been used up. Set the fish pies aside.
Heat a large cast-iron skillet with ½ inch oil over medium-high heat until hot (375℉/190℃) but not smoking.
Gently add the fish rolls to the hot oil and fry in batches, turning once, until golden brown, about 5 minutes. Avoid overcrowding the pan so it doesn't absorb excess oil and make greasy fish pies.
Remove the fish pies from the hot oil with a slotted spoon and drain them on paper towels. Serve warm or at room temperature.