Step 1Heat the oven to 425 degrees. On a floured surface, roll the puff pastry out to a rectangle about 10 by 20 inches; the dough will be just over one-eighth-inch thick.
Step 2To make the base of the tart, cut a rectangle out of the rolled dough measuring 6 by 16 inches and place on a parchment-lined baking sheet. To make the borders, cut 2 strips each measuring 1 by 16 inches, then cut 2 more strips, each measuring 1 by 4 inches.
Step 3Prick the base of the tart with a fork, and brush with the beaten egg. Place the borders on top of the base, lining them up with the edges of the base. Prick the borders with a fork, and brush with the beaten egg. Place the baking sheet in the refrigerator for 20 minutes to chill the dough before baking.
Step 4Remove the sheet from the refrigerator and place in the oven. Bake the shell until it is puffed and golden brown, 25 to 30 minutes. Remove and cool the baking sheet on a cooling rack.
Step 1Place the butter in a medium bowl; place a strainer in the bowl over the butter.
Step 2In a medium, heavy-bottom saucepan, whisk together the sugar and cornstarch. Whisk in the egg yolks, then the cream and milk. Whisk in the vanilla seeds and orange zest.
Step 3Place the saucepan over medium-high heat and cook, stirring constantly, until the custard begins to bubble and thicken, about 6 minutes. Remove from heat.
Step 4Immediately strain the custard into the bowl with the butter, stirring until the butter is melted and incorporated. Cover the surface of the custard with plastic wrap (to prevent a skin from forming) and set the custard aside to cool to room temperature, then refrigerate until needed. This makes a generous 1 1/2 cups pastry cream. The custard will keep, covered and refrigerated, for up to 5 days.
Step 1Make the glaze: In a small saucepan, combine the jelly and water over low heat. Cook, stirring frequently, until the jam warms and thins to a glaze-like consistency. Remove from heat and set aside.
Step 2Spread the pastry cream in the base of the tart shell in a smooth layer. (You might not use all of the cream. Any remainder will keep, covered and refrigerated, up to 5 days.) Arrange the berries over the top of the cream.
Step 3Brush the glaze over the berries, then sprinkle over the toasted almonds.
Step 4The tart can be served immediately, or chilled (uncovered) for up to 4 hours before serving.