1. Preheat oven to 425°F.
2. Unroll refrigerated Puff Pastry Dough and cut into three even pieces. Place dough on a baking sheet with the parchment paper and then poke all over with a fork. Cover with an additional piece of parchment paper and then place a baking sheet on top of parchment (pressing down lightly on top) and place in oven.
3. Cook for 15 minutes, then remove top baking sheet and top parchment and cook for an additional 5 minutes. Remove from oven to cool.
4. Make from scratch, or prepare to get pastry cream for filling the Napoleons.
5. When cool, cut each pastry section into four equal pieces. Top one piece of puff pastry with the pastry cream, cover second section with more pastry cream and stack on top. Repeat with all pieces, but keep 4 top layers for later.
6. To make the chocolate raspberry ganache: in a medium sauce pan, heat heavy cream and butter over medium heat (until almost boiling). Remove from heat and stir in chocolate chips, sugar, and raspberry preserves, whisking until smooth. Allow to cool slightly. then spread it over the third top pastry layer of the Napoleon, and place on top of the pastries. Garnish with raspberries or mint leaves.
For homemade Pastry Cream: Whisk together egg yolks and sugar. Heat milk in a medium sauce pan to just below boiling, remove from heat. Slowly pour milk into egg mixture, whisking constantly.Add cornstarch and whisk together. Pour mixture back into saucepan and return to medium heat, whisking constantly. When mixture thickens, turn heat to low and cook 2-3 minutes, whisking constantly to avoid lumps. Remove from heat and stir in butter and vanilla, whisking until smooth. Cool and cover with plastic wrap before refrigerating.