For filling

Cup of Yum
1. Make sure the pineapple has no tough core left or "eyes" then finely chop. Place the pineapple, sugar and lemon juice in a wide pot/saucepan and place over a medium heat. Warm, stirring now and then to mix and dissolve the sugar and bring to a simmer. Reduce heat as needed and simmer for around 25-30 minutes. Mash a little to help the pineapple break down a bit, and cook so it thickens and the mixture becomes quite jam-like. You should have very little liquid left.
2. Combine the corn starch and water and stir to form a slurry. Add it to the pineapple mixture, stirring immediately and mixing so that it is well combined. Cook for a minute or two more to let the mixture thicken up - it should be very thick. Set aside to cool. You should get around 1 ½ cups (360ml) of the pineapple mixture.

For pastry

1. Put the flour, baking powder, salt and cinnamon in a food processor and pulse to mix. Remove around 1 ½ - 2 tablespoon of the egg white and set aside, then add the rest along with the butter and milk. Pulse to mix and bring the mixture together in coarse crumbs.
2. Remove the dough from the food processor, press together and wrap then refrigerate for around 30 minutes, or more if it suit your timing better. You can make both the pineapple filling and pastry ahead.

Making the empanadas

1. Preheat oven to 400F/200C. Prepare a baking sheet/tray with either a silicone baking mat or parchment paper.
2. Roll out the dough on a floured surface until about as thin as you are comfortable with (around ⅛in/2-3mm) and cut out circles - I used my largest scone/pastry cutter which is about 2 ¾in (7cm) diameter.
3. Put roughly a rounded tablespoonful of the pineapple mixture slightly to one side of each pastry circle, but away from the edges. They should look as if they'll be fairly full but with enough space to fold one side over then seal the edges.
4. Carefully pull together the sides of the pastry and press the two edges together. This is easiest by folding over the side without the filling then pressing down the edge, taking care not to press out the filling or have an air bubble. Press together with the tip of a fork to seal. Alternatively, crimp the edges by folding over the edge, in towards the filling, and pressing with your thumb, then folding in the next edge again and again to form the braid-like edge.
5. Place the formed empanadas on top of the prepared baking sheet, with a little space between them. Brush the pastry with the reserved egg white (and add cinnamon sugar, if you like).
6. Bake for approximately 20 minutes until the empanadas are golden brown. If the filling has escapes a little, gently push it back in while still hot (then it will firm up and stay in as it cools). Allow to cool slightly before eating, or you can also eat them room temperature.