Make the dough: In the bowl of a stand mixer, combine the all-purpose flour, whole wheat flour, sugar and salt. Using the large holes of a box grater, grate the cold butter into the flour, then toss with the flour to coat. Attach the paddle hook and mix on low speed for 1 minute to blend the butter into the flour.

Stir together the water and vinegar. With the mixer on low speed, add the water and vinegar mixture to the flour a few teaspoons at a time, until the dough comes together in a shaggy mass. Stop the mixer. Gather the dough together, divide in half and shape each into a ball. Wrap each ball in plastic wrap. Chill for at least 2 hours and up to overnight.

Make the beef filling: Heat olive oil in your largest heavy pot over medium-low heat. Add the red and white onions and cook until the onions are soft, about 10 minutes, stirring occasionally.

Add the garlic and beef and break the meat into small mince using a wooden spoon. Increase heat to medium and brown the beef with the onions for an additional 10 minutes, stirring frequently.

Tumble in the chopped tomatoes, salt and pepper; stir the filling very well. Cook for 30 to 40 minutes, until the tomatoes have cooked down and the liquid has evaporated. Turn off heat and stir in green onions. Spread the mixture on a rimmed baking sheet to cool completely. Refrigerate if you have space.

Preheat oven to 350°F (180°C).

Make the empanadas: Roll out one ball of the dough to 1/16-inch (2 mthickness. Using a 4½-inch (11 cround cookie cutter, cut out 18 to 20 circles. (You may find it easier to pinch off golf ball–size pieces of dough and roll them individually.) Place a generous tablespoon of filling in the centre of each dough disc. Top with a small piece each of hard-boiled egg and olive. Brush the edges with the egg wash. Fold one edge over the other, keeping the filling tucked into the centre, and press the edges together to form a half moon. You can seal the edges by pressing them with a fork, or you can make a traditional empanada twist by folding the edges over and crimping in place (this takes practice!).

Place empanadas on a baking sheet, about an inch (2.5 capart. Brush with egg wash. Bake for about 40 minutes, until deep golden brown. Repeat with remaining ball of dough and filling. Also re-roll any scraps of dough and fill. Enjoy baked empanadas hot and cool the remainder on a wire rack.