A classic tart made with a buttery, flaky crust and creamy, dreamy strawberry rhubarb curd filling. Topped with a creamy vanilla bean mascarpone frosting and fresh strawberries.
Combine cut strawberries, rhubarb, water, and lemon zest in a 1.5 quart saucepan and bring to a boil on medium-high heat, stirring frequently to ensure the mixture doesn't stick to the bottom of the pan and burn. Once boiling, reduce to medium-low heat to continue to break down the fruit.
Once the fruit is broken down and very soft (puree-like) remove from heat. Strain mixture through a medium mesh sieve to remove the larger fruit pulp and a second time through a fine mesh sieve to get the mixture to be purely fruit juice with no seeds. This should yield more than 1/2 cup of liquid to ensure you have enough for the tart.
Remaining puree topping (optional): The strained leftovers of strawberry & rhubarb puree can be mixed with 1/2 cup of powdered sugar and used as a delicious topping for this tart for extra flavor or as a fruit filling in another pastry recipe.
In a medium heatproof mixing bowl, place eggs, sugar, strawberry rhubarb juice and heavy cream, if using, and whisk to combine. Place the bowl over a saucepan of simmering water (bain-marie). Cook on moderate heat, whisking constantly, until mixture becomes thick (mine was ready in 10 minutes, but it can take up to 20). If you have a thermometer, it should register 170°F/75°C; otherwise, it should coat the back of a wooden spoon and leave a clear pass if you run your finger through it. The curd will thicken more once cooled.
Remove from heat and immediately strain mixture through a fine mesh sieve. Add butter, a few cubes at a time, and whisk until completely melted and incorporated, and mixture is smooth. Take your time with it—the whisking makes for an airy and light texture. Allow to cool to room temperature before filling the tart. (Curd can be kept in an airtight container in the fridge for up to a week. Whisk the mixture to smooth it before using.)
Fill the tart shell with strawberry rhubarb curd, then refrigerate for at least 5 hours until chilled. Serve with berries, whipped cream, or whipped mascarpone frosting if you like. The tart is rich, so cut your servings small.
Whipped vanilla bean mascarpone frosting recipe can be found here.