In a large skillet, saute the precooked beef and pork cubes, onions and garlic in the butter over high heat for 5 minutes, until the onions are golden brown.
Add the red wine to deglaze the pan, loosening any browned bits on the bottom of the pan with a wooden spoon. Add the mushrooms, basil, parsley, thyme, salt, pepper, and cook until the liquid has evaporated.
Stir in the demi-glace and cook about 5 minutes more, until all liquid has evaporated again. Remove from the heat. Spread the mixture out onto a baking sheet and let it cool for about 10 minutes. Refrigerate the mixture about 1 hour to cool completely. Preheat oven to 450 degrees F.
On a lightly floured surface, roll out the puff pastry to 1/8-inch thickness. Cut out 6 (6 to 8-inch) squares and brush the edges with the egg mixture. Place 1 cup of the meat mixture in the center of each square. Fold each square over diagonally to form a triangle and press the edges firmly to seal. Using a fork, gently prick the center of each triangle to allow steam to escape. Lightly brush the edges again with the egg mixture. Arrange the triangles 2-inches apart on a greased baking sheet.
Bake for 8 to 10 minutes, until golden brown.
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.
Recipe courtesy of City Tavern, Philadelphia