I cannot stress how naughty this dessert it. SO. MUCH. SIN.
It's got butter, white and brown sugar, copious gooey fruit, and the crust I used is a lard dough that my grandfather sent me the recipe to. (I was living in Germany at the time and was in dire need of American apple pie!) The flaky crust, the oozing, syrupy fruit (with a hint of balsamico), the crunch of the streusel topping, and a dollop of Mascarpone whip is truly a taste-texture explosion. It is sincerely one of the best pies I've made in a while.
Here's the recipe, which I adapted from another recipe I found online.
For the crust:
1 unbaked pie crust of your choice (I used my grandfather's recipe, but most people I know have their own favorites)
For the filling:
6 stalks fresh rhubarb, sliced in 1/2" chunks
1-1/2 cups fresh strawberries, sliced
3/4 cup sugar
1 TB balsamic vinegar
3 TB arrowroot or cornstarch (your pie will be a soupy mess without this!)
For the streusel topping:
1 cup flour
1/2 cup brown sugar
1/2 cup butter, cold and cut into pieces
For the Mascarpone whip:
8 ounces Mascarpone cheese
1 cup heavy cream
1/2 teaspoon vanilla
1/2 cup + 2 TB sugar
In a large bowl, combine rhubarb, strawberries, sugar, balsamic, and arrowroot (or cornstarch). Stir well until the strawberry-rhubarb mixture is syrupy.
In a small or medium bowl, add the butter pieces, the flour, and the brown sugar, and using a pastry cutter, incorporate the butter into the flour/sugar mixture until crumbly.
Preheat oven to 400 degrees F. Roll out the pie dough and place into a 9-inch pie pan. Pour the strawberry-rhubarb mixture into the pie pan, evening out the contents with a spoon. Take the streusel topping and spread evenly across the top of the pie, covering as much of the strawberry-rhubarb mixture as possible.
Bake at 400 degrees for 50-55 minutes, covering the pie with foil halfway after 30 minutes to prevent over-browning.
While the pie is baking, make the Mascarpone whip. Take the heavy cream and beat until the cream forms stiff peaks. Transfer whipped cream into a clean bowl. Take the Mascarpone and place into the same bowl you used to beat the cream and mix with vanilla and sugar. Beat the Mascarpone-sugar mixture until well aerated, about 2-3 minutes. Add the whipped cream to the Mascarpone, a little bit at a time, until it is well incorporated. Chill until time to serve.
When the pie is done, let cool for two hours, and serve with a large dollop of chilled Mascarpone whip.