Lemon-Rhubarb Icebox Cake

Start to finish: Active: 1 hour 15 minutes
Impresses: 4-6

Ingredients
For the rhubarb jam:
3 cups chopped rhubarb
1½ cups granulated sugar
Juice of 1 lemon
1 tablespoon vanilla extract
½ teaspoon kosher salt

For the lemon curd:
1 cup lemon juice
½ cup granulated sugar
1 egg
4 egg yolks
Pinch of kosher salt

For the lemon custard:
1¼ cups half & half
1/3 cup sugar
3 egg yolks
1½ tablespoons cornstarch
½ teaspoon kosher salt
2 teaspoons lemon zest
1 tablespoon unsalted butter, softened
1 teaspoon vanilla extract
¼ teaspoon lemon extract
1 cup heavy cream
2 tablespoons powdered sugar

For the icebox cake:
1 package lemon shortbread cookies
1½ cups heavy cream
¼ cup powdered sugar
¼ teaspoon lemon extract
1 teaspoon lemon zest

Method
For the rhubarb jam:
Combine all ingredients for the jam in a large pot. Cook over medium heat, stirring occasionally, until reduced and thick, about 20 minutes. Remove from heat and allow to cool to room temperature.

For the lemon curd:
Whisk together lemon juice, sugar, egg, egg yolks and salt in a shallow saucepan until smooth. Set over medium-low heat and cook, stirring occasionally, until thickened, about 5 minutes. Be sure curd does not scorch to the bottom of the pan or boil too vigorously. The curd is done when it coats the back of a spoon and holds a line when streaked with a finger. Remove curd from heat and pour through a fine mesh sieve into a glass bowl. Cover with plastic wrap, and set aside until cooled to room temperature.

For the lemon custard:
Pour half & half into a medium saucepan and set over medium-low heat. In a glass bowl, whisk together sugar, egg yolks, cornstarch and salt until thick and pale yellow, about 2 minutes. When half & half is steaming, pour a thin stream into the sugar and egg yolk mixture while whisking constantly to temper the eggs. Whisk until smooth before pouring mixture back into saucepan.

Cook custard, gently stirring constantly, until thick enough to hold the outline of a figure 8 made with a spoon. Remove from heat and whisk in lemon zest, butter, vanilla extract and lemon extract. Pour into a clean glass bowl and cover with plastic wrap. Set aside until cooled to room temperature.

When custard is room temperature, whip heavy cream and powdered sugar to medium peaks. Gently fold whipped cream into the custard and set aside.

For the icebox cake: 
Line a 9-by-5-inch loaf pan with plastic wrap on all sides, making sure to leave an overhang on the long sides of the pan to wrap the top of the cake.

Place a layer of shortbread cookies in the bottom of the pan, breaking or cutting the cookies to make them fit in an even layer. Top with a layer of lemon custard, about 1½ cups, followed by ¼ cup lemon curd and ¼ cup rhubarb jam. Repeat the process of layering the cookies, custard, curd and jam 2 more times. Top with a final layer of custard and then a final layer of cookies. Wrap plastic wrap over the top of loaf, and refrigerate for at least 12 hours.

When ready to serve, whip the remaining heavy cream, powdered sugar, lemon extract and lemon zest until thick. Unwrap the cake and invert the pan on a serving platter.

Remove the pan and plastic wrap from the cake, and cover with the lemon whipped cream. Garnish with more zest and crumbled shortbread cookies to serve.