Remove any tough stems from spinach and wash thoroughly. Then fill a big pot with water and bring to boil at medium heat. When the water is boiling, add a pinch of salt and the spinach. Cook for 1 or 2 minutes, then remove from heat. Drain the spinach and rinse with cold water to stop the cooking process. Squeeze as much of the water from the spinach as possible
Then, finely chop the spinach and mix into the ricotta. Add salt, black pepper, and nutmeg to taste. Set aside.
Mix the flour with a pinch of salt and baking powder. Now melt the butter and pour it into the mixture, while adding a cup of warm water. Mix gently until you get a dough.
Let the dough rest for 10 minutes inside a plastic bag.
Turn dough out onto a floured work surface and stretch it with a rolling pin into a round about 0.2 inch thick. Now cut 6 circles roughly 2 inches in diameter each and brush the corners of every circle with some beaten egg.
Now fill the center of every circle with about a half tablespoon of the spinach mixture and close it making a half moon shape. Pay close attention to the corners to make sure they are completely sealed. You can secure the corners by pressing gently with a fork. Once sealed, brush the tops of the empanadas with the beaten egg.
Put the empanadas in an oven pre-heated to 392ºF for 8 minutes or until they´re golden brown.