Because the pastry cream needs to be removed from the saucepan immediately, prepare a medium sized bowl, a fine mesh strainer or a food mill, and a heat resistant rubber spatula near the stove.
In a large bowl, whisk together the flour with 1 cup of the sugar as well as the eggs until incorporated. The mixture will be very thick.
In a medium saucepan over medium heat, combine the milk, the remaining cup of sugar and the salt. With a pairing knife, scrape the inside of the vanilla bean and place contents into the saucepan. Cook the mixture, stirring occasionally to prevent scalding. Remove from heat when the milk just begins to simmer. While whisking constantly, slowly pour about half of the milk in a thin stream into the flour mixture. Once the 2 mixtures are combined, continue whisking the combined flour and milk and return the contents to the saucepan with the remaining milk. Place the saucepan on medium heat while whisking constantly. Cook the mixture until it thickens, approximately 2 minutes. Immediately remove the pan from the heat as soon as the first bubble breaks the surface of the pastry cream.
Pour the hot pastry cream into the strainer or food mill over a medium sized bowl. With a spatula, push the cream through the strainer or food mill. To prevent a skin from forming, place plastic wrap directly on the surface of the cream and refrigerate for 3 to 4 hours, or overnight.
Have packaged puff pastry unrolled on cutting board. Bake the puff pastry according to package directions. Spread layers of pastry cream between the baked puff pastry alternating optional flavors. Garnish with fruit or nuts and sprinkle with powdered sugar.
For a unique look, cut out shapes in the puff pastry with cookie cutters. Puff pastry comes frozen from the grocery store, so thaw in the refrigerator several hours or overnight before using. Dip your cookie cutters into some flour before using to prevent them from sticking to the dough. When you cut out shapes in puff pastry with cookie cutters, make sure you just push down on the cutter, and then up. Do not twist the cutter back and forth in the puff pastry as this will seal the sides and will prevent the pastry from rising to its maximum. Flavor your pastry cream with strawberry jam or ground pistachios, or chocolate and add to taste. If you want brighter colors add a drop of food coloring. To add the chocolate, take a small amount of the pastry cream designated to be flavored chocolate and thoroughly mix in the warm chocolate. Mix this pastry cream into the remaining pastry cream. Mixing the warm chocolate into the smaller amount of pastry cream helps ensure the chocolate will mix in smoothly and completely.