To make the crust, put the flour, salt and sugar in a food processor, pulse to combine. Add the cold butter and process until you have fine crumbs.
With the motor running, add 1 tbsp of ice water at a time until the dough starts to come together. It’s unlikely you will need all 120ml of the water, just add until the dough is starting to clump.
Carefully (haha) remove the dough from the food processor and form into a ball. Cut the ball into two and flatten into two discs. Wrap in cling film and chill in fridge for 1 hour. Remove dough from fridge about 10 minutes before rolling.
Put the Nutella in a bowl and stir in the cinnamon and chili until combined. Set aside.
Preheat the oven to 200C/400F and line baking sheets with parchment paper
Roll out the pie dough about 3mm thick and cut out 3 inch circles, place the circles on the lined baking sheets. Keep rolling out the dough as many times as you need to to cut as many circles as you can.
Place about 1/2 tsp nutella on one half of the circle and top with a slice of banana. Fold the over half over and pinch the edges to seal, crimp closed with a fork. Repeat with all circles.
Brush each empanada with a little melted butter and sprinkle on cinnamon sugar. Bake for 18-20 minutes, until golden brown.
Cool on a wire rack, enjoy warm or at room temperature.
*Measure out 120ml water and add a few ice cubes, swirl around and leave to sit for 5 minutes so the water is nice and cold!