Here is a quick tutorial on how to make napoleons. I didn't include recipes with this because it's a lot to type right now. I used pre-made puff pastry, but I did make the diplomat cream and glazes from scratch. I made two half-sheet pans of pastry which gave me two napoleon logs.
Start with one sheet of puff pastry, thawed and unfolded. Use flour or parchment paper to roll out to the size of the sheet pan. I cut a piece of parchment the size of the pan and used it as a guide to roll out the pastry. Silpats can be used instead. Dock the pastry generously.Cover pastry with another piece of parchment, then put another sheet pan that is the same size over top of the pastry. This will prevent the pastry from rising too high in the oven and promote even baking.
Bake for 20 minutes at 375 degrees, then take pan and parchment off the top and return to oven for 7-10 minutes to allow the pastry to brown. It should look dry and flaky. Yum!
Trim the edges of each pastry and cut into three even rectangles.
Place one rectangle on a piece of cardboard. Avoid using a plate if it has any curve to the edges as the pastry is very fragile and will break off if not placed carefully on a very flat surface.
Pipe a dam of diplomat cream around the edges of the first layer of pastry. I piped it twice to make sure it would be tall enough to hold all of the delicious cream.
Fill in the dam with diplomat cream and smooth.
Repeat with second layer of pastry and place last on top. The cream will more like ooze out around the edges even with use of a dam.
Use a spatula or flat knife to scrape the sides. Try to get the extra cream off without breaking the edges of the pastry.
Wrap both logs tightly in plastic wrap and freeze overnight. I put the logs in the freezer unwrapped for about 10 minutes to get it to firm up so that I could wrap it without making a mess. You can use a spatula to transport it to the plastic wrap.
After freezing overnight, take logs out to thaw for about a half hour. You shouldn't try to glaze them if they are too cold because it will cause the glaze to harden too quickly and make it difficult to get a smooth top. I used scissors to cut away the plastic wrap to prevent damage to the logs.
Get your glaze ready. I used the same glaze for this as I do my cream puffs so I didn't show how to make this. Just refer to my cream puff tutorial. I put the white glaze in a piping bag and cut a small tip.
Use a spatula to spread the chocolate glaze over the napoleon. Try to get it as smooth as you can. My napoleons were still a little too cold and made this hard for me. Then pipe lines with the white glaze and use a paring knife or toothpick to drag through the lines, alternating directions, to get a nice design.
Here is what it should look similar to. You could always pipe the lines smaller and closer to get a finer tuned design.
Place the napoleon back into the fridge or freezer to firm it up, then cut into slices.