1scant pint strawberries, hulled (quartered if large, halved if medium, left whole if very small(1 1/2 cups cut)
seeds from 1/2 vanilla bean
zest of 1/4 of a (meyer)lemon
1cupcrème fraîche, divided use
Make the crust:
In a large bowl, stir together the flours, sugar and salt. Scatter the butter pieces over the flour, and rub in with your fingertips until the mixture resembles sand with lots of pea-sized butter chunks. Stir together the buttermilk and ice water. Drizzle this mixture over the flour mixture, 1 tablespoon at a time, tossing with a rubber spatula, until the dough will hold together when you give it a squeeze, adding more ice water by the teaspoon directly to the dry bits as needed.
You can call it here, or you can do either or both of the steps below for extra flake:
Option 1 - fraisage:
Dump the dough out onto a counter, divide it roughly into 8 portions, and fraisage by dragging a portion of dough across the counter using the heel of your hand. Scrape up the dough (a metal bench scraper works well here), gently press it into a ball and flatten into a disc. Slip it into a plastic bag, and chill for at least 30 minutes or up to 2 days.
Option 2 - roll, fold, roll:
On a lightly floured surface, roll the chilled dough out into a rough square that is about 1/4" thick. Fold it in thirds like you're folding a letter, then roll up from a skinny end into a loose spiral. Gently press to flatten it slightly, and chill for 30 minutes to 1 hour.
Remove the dough from the fridge, unwrap, and place on a lightly floured surface. Roll out the dough into a 12" circle, dusting the dough lightly with flour as needed, rotating and flipping it to prevent it from sticking. Ease the dough into a 9" glass pie plate, fit it into the corners, and trim it to a 1" overhang. Fold the overhang under, and flute the crust by pressing it between the thumb of one hand and the index finger and thumb of the other hand. Prick the dough all over with a fork.
Chill the crust for 20 minutes, then freeze it for at least 20 minutes, until solid.
Position a rack in the lower third of the oven and preheat to 400º.
Place the frozen crust on a rimmed baking sheet. Line it with a piece of parchment paper or foil, and fill with pie weights, dry beans, or clean pennies, pressing the weights into the sides and corners of the crust.
Bake the crust for 15-20 minutes, until the dough will hold its shape when you lift off the parchment, then remove the weights and parchment and bake until the bottom is dry and lightly golden, about 5 minutes longer. Reduce the oven temperature to 375ºCool the crust slightly.
While the crust bakes, make the streusel:
In a medium bowl, combine the powdered sugar, baking powder, salt and flour. Add the butter cubes, and work with your fingers or a pastry blender until it begins to clump together. Set aside. (You'll use the brown sugar and oats later.)
While the crust cools, make the filling:
In a large bowl, rub the vanilla bean seeds, lemon zest and salt into the sugar until combined. Toss in the rhubarb and strawberries to coat.
Assemble the pie:
Spread 1/4 cup of thecrème fraîche in the bottom of the cooled pie crust. Sprinkle 1/2 cup of the streusel over thecrème fraîche. Mix the brown sugar and oats into the remaining streusel. Pour the strawberries and rhubarb into the pie and top with any extra juices. Dollop the remaining 3/4 cup crème fraîche over the fruit, then sprinkle evenly with the remaining streusel.
Bake the pie:
Criss-cross two long pieces of foil on a baking sheet, set the assembled pie in the middle, then fold the foil up and over the crust, scrunching as necessary so that the foil just covers the crust and leaves the filling exposed. Bake the pie until the streusel is golden all over and the fruit is bubbling, about 90 minutes. Rotate the pie halfway through for even baking. Let cool at least 1 hour, then serve warm or at room temperature.
The pie is best the day it has been baked, but will keep for 24 hours at cool room temperature, or up to a few days in the fridge.
Adapted from this Nectarine Crème Fraîche Pie which was adapted from Deb who adapted it from Martha.I like this pie best shortly after being baked, but I've been known to swipe slices straight from the fridge on days 2 and 3. The crust can be par-baked in advance and stored for a few days in the fridge, and the streusel can be made a day ahead and stored at room temperature.You may wish to make a double batch of pie dough, especially if you do the fraisage and folding options described below for extra flake, and save half of it in the freezer for a future pie. For step-by-step photos for making super flaky, all-butter, semi-whole-grain pie dough, check out my pie dough tutorial.You can make your own crème fraîche by stirring 1 tablespoon buttermilk into 1 cup of heavy cream. Cover and let sit at room temperature for 24 hours until thickened. Stir, then refrigerate for up to a week or two. Though feel free to use sour cream in its place (and let me know how it works - I'm curious!).This pie likes a long bake, so be sure to protect the edges of the crust with foil (as shown in the tutorial) to prevent them from become overly-caramelized.Nutritional values are based on one of ten servings.