Pour the sweetened condensed milk into a non-sick sauce pot. Simmer the sweetened condensed milk over low heat for 20-30 minutes, stirring often to ensure the sauce is not burning. Once the sauce turns a very light shade of caramel stir in 1 teaspoon vanilla and remove from the heat.* Set aside to cool. The condensed milk will thicken as it cools.

Add the butter to a large skillet and set over medium heat. Add the apples and cinnamon, stirring to combine. Cook until the apples are soft, about 8 minutes. Remove from the stove and stir in the melted butter. Allow the apples to cool completely before assembling your pies.

To make the crust. Place the all-purpose flour and the salt in a large bowl. Add butter and use your fingers to break the butter into the flour until mixture resembles small peas. Whisk the egg yolk with 1/4 cup cold buttermilk in a small bowl and then add the egg mixture to the flour mixture. Mix with a wooden spoon, drizzling in more buttermilk as needed (no more than 1 tablespoon at a time), until dough just comes together (a few dry spots are ok). Gently knead dough on a lightly floured surface until no dry spots remain, about 1 minute. Divide dough in half. Shape each piece into a circular disk.

Roll out 1 disk of dough onto a lightly floured surface to a 16-inch round. Using a three inch circle cookie cutter, cut out as many circles from the dough as you can. Repeat with the remaining piece of dough. I was able to get 16 rounds (for a total of 8 pies).

Line two baking sheets with parchment paper.

Once everything is cool, begin assembling your pies. Spread a round tablespoon of the caramelized sweetened condensed milk on one half of the pie crust rounds, leaving a 1-inch boarder around the edge. Add a round tablespoon of the apples atop the condensed milk.

Place the remaining rounds of pie crust over the apples, stretching the dough just slightly if needed to fit. Use a fork to crimp around all the edges. Place the pie on the prepared baking sheet. Cover the pies with plastic wrap and place in the fridge for 45 minutes or up to 2 days.

After 45 minutes, preheat the oven to 350 degrees F.

Remove the pies from the fridge and brush with the beaten egg. Cut 4 small slits in the top of each pie. Bake for 25-30 minutes or until the pies are golden brown. Some of the pies may be oozing a little when you take them out. This is fine.

Brush the warm pies with melted butter and sprinkle each generously will cinnamon sugar. Serve warm or at room temperature.