Mix all-purpose flour, corn flour, baking powder, curry powder and salt in a bowl. Add canola oil. Add 1/2 cup of water, mixing with your hand. If the dough feels too dry and difficult to process, add water 1 tablespoon at a time until you get a pliable texture. Shape the dough into a ball and wrap tightly in plastic wrap and place in the refrigerator for the time you take making the filling.