Recipe

Black & Blue Pie

A delicious ode to summer’s bounty—and to love

By Brigid Washington
Recipe by Keia Mastrianni

August 17, 2022

Photo: Keia Mastrianni

For Keia Mastrianni, the owner and head baker of Milk Glass Pie in Shelby, North Carolina, a side hustle that grew alongside an improbable romance formed her path to professional pie baking. “As a food writer, I was constantly in orbit with so many talented and inspiring chefs, bakers, farmers, and artisans,” Mastrianni remembers. “I pitched a profile of a local farmer—Jamie Swofford—and from that chance interview, for a publication that’s now defunct, Jamie’s and my relationship grew and evolved, and now we’re husband and wife.”

As Mastrianni’s love for baking burgeoned, she created a cottage bakery space on her and her husband’s farm. But the question of whether to continue her writing career or take up the pursuit professionally nagged—up until the pandemic-induced lockdown answered. During those dreadful early days, to maintain connections and to soothe, Mastrianni baked pies and delivered them to the porches of friends and neighbors every Friday. “Word spread, orders quadrupled, and my pandemic pie project that I referred to as Front Porch Pie grew exponentially,” Mastrianni says of the happy surprise. “That little community exercise gave me the answer I needed, which was to bake.”

Today, Mastrianni’s pie business is her bread and butter. Her pies amplify the connection between farmer and baker and are painstakingly crafted, with an astonishingly high level of detail. At the heart of each one lies her ability to focus and compound flavors, which this Black & Blue summer pie highlights.

It all starts with a rye crust. Mastrianni acknowledges that some home bakers may be unfamiliar with making a pie crust with rye flour, but the incorporation of a whole grain flour, with perceptible hints of bran, endosperm, and germ, assures an even more delicious outcome than solely using a less nuanced all-purpose white flour. “The use of rye flour, especially in a juicier berry pie, creates a wonderful contrast,” notes Mastrianni, who believes baking is especially rewarding when all five senses are engaged. “The rye crust is earthy and toothy.”

One practical tip she champions: using time and the high-climbing heat of the oven well. “Over the years, I’ve noticed that people aren’t baking pies long enough,” Mastrianni says. “I think people fear burning a pie, and often pull it before it’s had the necessary time to cook completely, which can result in a pale pie with an undercooked filling. Be bold when baking a fruit pie.” And don’t get discouraged; after all, as Mastrianni happily exclaims, “practice makes pie!”

Ingredients

Black & Blue Pie (Yield: 1 9-inch double-crust pie)
For the crust:
- 1½ cups all-purpose flour
- 1 cup rye flour
- 1 tsp. kosher salt
- 1 tbsp. sugar
- 2 sticks unsalted butter, straight out of the refrigerator
- 1 tbsp. apple cider vinegar
- Ice cold water
- 1 egg yolk
- 1 tbsp. heavy cream
- Demerara sugar, for sprinkling
For the filling:
- ¾ lb. blackberries, about 2½ cups
- 1 lb. blueberries, about 3 cups
- 2 tbsp. lime juice
- ½ vanilla bean
- ¾ cup granulated sugar
- Zest of 1 lime
- 3 to 4 lemon verbena leaves, finely chopped (optional)
- ¼ teaspoon salt
- ¼ cup tapioca flour

Preparation

Make the crust: Whisk together both flours, salt, and sugar. Add the cold butter to the flour mixture and use a pastry cutter or bench scraper to cut the butter into the flour. Begin using your fingers to smoosh the butter in flat pieces. Continue coating butter pieces in flour. Work the butter until there are no large pieces of butter visible. It’s okay to have varying sizes of butter, but make sure that the huge chunks have been worked into the flour. It should look like sand with small pebbles in it.

Mix apple cider vinegar and ice water together to equal ½ cup total liquid. Make a well in the center of the flour/butter mixture and add half of the liquid. Toss flour with liquid until it is fully incorporated, then add the remaining liquid.

Use your hands to work the dough, but do not knead it. The dough will become shaggy. Once it begins to hold its shape, begin lightly pressing into two discs. Dump out onto the work surface and continue shaping dough into discs. If the dough looks dry, add more water, one tablespoon at a time.

Wrap and refrigerate for at least 1 hour, or overnight.

Make the filling: Wash berries and strain excess water through a colander, giving them a good firm shake. Combine in a large bowl and add the lime juice. Scrape the seeds of one-half of a vanilla bean into the granulated sugar, then add the zest of one lime and, if using, the lemon verbena leaves. Use your hands to rub the vanilla bean, zest, and lemon verbena into the sugar, releasing the citrus oils and infusing the vanilla and herbs into the sugar. Add salt and tapioca flour and toss to combine. Just before filling the pie shell, toss the berries with the sugar mixture and add to pie shell.

Assemble the pie: Once the dough is chilled, transfer to a lightly floured surface. Roll out the top crust first, into a 10-by-12-inch rectangle. It should be long enough to span the circumference of the pie tin and wide enough to cut lattice. Cut six wide strips, about 1½–2 inches wide. Place on a parchment-lined baking sheet and chill while you roll out the bottom crust.

Roll the bottom crust to fit the 9-inch pie tin, leaving a 1-inch overhang. Fill pie tin with berry mixture and arrange the lattice topping: Place three vertical strips of dough on top first. Fold center strip back and lay the first horizontal strip on the pie. Repeat the process, folding back two outside vertical strips and laying the outside horizontal strips onto the pie. Trim the lattice edges flush with the edge of the pie tin. Roll the bottom overhang on top of the pie tin edge to seal the lattice edges and create the crust. Preheat the oven to 400°F.

Make an egg wash by whisking together egg yolk and cream. Brush entire pie with egg wash and sprinkle it with demerara sugar. Place in oven for 20 minutes, until the crust begins to take on color. Reduce oven temperature to 375°F degrees and bake for 45 more minutes, until the filling is bubbling and the crust is golden brown. Let cool for at least 3 hours, or overnight for best results.