How to Make It
Preheat the oven to 375°. Line a large baking sheet with parchment paper. On a lightly floured work surface, roll out the puff pastry to a 12-by-6-inch rectangle. Trim the pastry into 4 neat rectangles, 6-by-3 inches each. Cut each rectangle into 3 equal pieces and transfer them to the prepared baking sheet. Chill for 10 minutes. Poke each piece 3 times with a fork. Cover the pastry with parchment paper and top with another baking sheet to prevent the pastry from puffing. Bake for about 35 minutes, until the pastry is deep golden and crisp. Remove the top baking sheet and parchment and let the pastry pieces cool completely.
Meanwhile, in a medium saucepan, bring the milk and sugar to a simmer. Add the lemon verbena and the vanilla bean and seeds. Remove from the heat, cover and let stand for 15 minutes. Strain the milk into a heatproof measuring cup.
In a medium bowl, whisk the egg yolks with the cornstarch and flour. Gradually whisk in the hot milk. Pour the mixture into the saucepan and cook over moderate heat, whisking constantly, until the pastry cream is very thick, about 4 minutes. Transfer the pastry cream to a bowl.
In a small glass bowl, sprinkle the gelatin over the water and let stand until softened. Microwave the gelatin for 5 seconds, or until melted. Whisk the gelatin into the warm pastry cream. Press a sheet of plastic wrap directly onto the pastry cream and refrigerate for about 1 hour, or until it is thoroughly chilled.
In a medium bowl, using an electric mixer, beat the heavy cream until stiff. Beat half of the whipped cream into the pastry cream. Fold in the remaining whipped cream with a rubber spatula. Refrigerate the pastry cream until chilled.
Arrange all of the puff pastry pieces on a work surface. Brush 4 of the pieces with the raspberry jam and the remaining 8 pieces with the apricot jam. Spoon a scant 1/4 cup of the pastry cream onto the 4 raspberry-topped pieces and 4 of the apricot-topped pieces. Arrange the strawberries over the cream filling; reserve 4 of the whole or sliced strawberries for garnish. Dollop any remaining cream over the strawberries. Stack the raspberry layers on top of the cream-filled apricot layers, pressing lightly. Top the stacks with the remaining apricot-topped layers. Refrigerate the napoleons until chilled, 4 to 6 hours. Garnish the napoleons with the reserved strawberries and serve.
Fresh lemon verbena is available at farmers' markets and at specialty food stores. Dried, whole lemon verbena leaves can be found wherever fine teas are sold.