Mix the flour and salt in a large bowl to combine.
Add the melted butter, egg yolks, and water to the flour mixture.
Mix until the dough begins to form. Transfer to a dusted flour surface and continue to knead until a consistent ball of dough forms. If the dough feels too wet, add flour one tablespoon at a time until it no longer sticks to your hands.
Cover the dough with a towel and let chill in the fridge for at least 30 minutes.
Divide the dough into quarters, then into eighths, then sixteenths. Roll each piece into a ball. On a flour dusted surface roll each ball into a round circle using a rolling pin.
For the Filling / Assembly
Combine brown sugar and granulated sugar in a medium bowl. Set aside.
Peel and core apples. Chop into ¼ cubes. Set aside.
In a saucepan combine brown sugar, cinnamon, salt, and butter over medium-low heat. Cook until the butter and sugar become liquid and bubbly.
Add the apples to the pan and toss gently to coat with the sauce. Cook for a few minutes before adding the cornstarch slurry and toss again to coat.
Once filling begins to thicken and the apples begin to soften, remove from heat and set aside to cool.
Once cool, add a tablespoon or two of the filling into the center of the empanada discs.
Brush a small amount of water on the lower half of the empanada disc. Fold empanada dough over so it meets the moistened half of the dough. Press lightly with fingertips.
Using a fork, press the empanada dough to seal and crimp the edges shut.
Heat 2/3 cups of oil in a frying pan to around 350°F and fry empanadas on each side until golden brown and crispy on the outside. Use more oil if needed.
Once fried, brush both sides of the empanada with melted butter and roll in the cinnamon / sugar mixture.