Mix together the filling ingredients in a bowl; make sure they’re well mixed.
Grease a mini muffin pan, and line each mini pan with pie dough so it looks like tiny pie crusts. Fill each mini pie crust with about 1 spoonful of filling. You'll probably have extra filling, it's okay, freeze it and save it for later.
Once each one is filled, lay a tiny piece of pie dough over each one. If it doesn't completely cover it, it's not a huge deal.
Mix the egg yolk and butter together, brush each mini pie with this. It'll give your pies a golden color.
Bake in the oven for 20 to 30 minutes.