6 cups rhubarb, sliced on a diagonal into 2.5 centimeter pieces
One 8 centimeter piece ginger, peeled and thinly sliced
For the tiramisu cream filling
3 large egg yolks
1/3 cup sugar
1 teaspoon powdered ginger
2 tablespoons dry Marsala wine
2 tablespoons orange liqueur
1/2 teaspoon vanilla extract
1 teaspoon orange zest
2 cups mascarpone cheese
3/4 cup chilled whipping cream
1/4 cup boiling water
1/2 teaspoon powdered ginger
1/2 cup orange juice
1/2 cup liquid from roasted rhubarb
1 tablespoon orange liqueur
20–24 store bought ladyfingers
1 cup chopped pistachios
To prepare the rhubarb, stir together the sugar, orange zest, and the pulp from the vanilla bean in a medium mixing bowl. Add in the rhubarb, sliced ginger, scraped vanilla bean pod, and the juice of the orange into the bowl and stir well to combine. Allow this to sit at room temperature for 25–30 minutes to allow the rhubarb to release some of its juices.
Meanwhile, preheat the oven to 350F. Roast the rhubarb, tossing once about halfway through, for 20–25 minutes or until tender and juicy. Allow the rhubarb to cool to room temperature.
For the tiramisu cream filling, in a large glass or metal bowl, whisk together the egg yolks, sugar, powdered ginger, marsala, and orange liqueur together. Place over a pot of simmering water and whip using a wire whisk or handheld electric mixer until the mixture has tripled in volume (this should take around four to eight minutes). Remove the bowl from the heat and beat in the vanilla and mascarpone. Allow the mixture to cool to room temperature then fold the whipping cream into the mascarpone mixture.
For assembly, stir together the boiling water and powdered ginger in a shallow dish. Add in the orange juice and orange liqueur. Set out eight individual serving dishes and quickly dunk the ladyfingers in the orange ginger mixture until they are lightly soaked. Break a ladyfinger or two into each serving dish, top with a generous helping of the mascarpone mixture, a spoonful of the rhubarb, and a scattering of pistachios, and then repeat the layers.
Serve immediately or place in the fridge to firm up before serving.