1 lb frozen Oregon strawberries
1 C sugar
½ t vanilla (optional)
2 ½ C all-purpose flour
½ t kosher salt
2 T sugar
1 C (2 sticks) cold unsalted butter, cut into ½” cubes
¼ C milk plus extra for brushing
2 T ice water (plus extra as needed)
1 C powdered sugar
2-3 T milk
¼ t vanilla
1. In a small heatproof, nonreactive pan, sprinkle the strawberries with the sugar and vanilla and thaw overnight. The next day, bring to a low boil and simmer over medium heat for about 25-30 minutes (mashing the berries into jam along the way), until the mix becomes very jammy or reaches the setting temperature of 220°F. It will thicken as it cools.
2. While the jam is cooking, prepare the pastry. Mix the dry ingredients together, then cut in the cold butter using either a food processor, pastry cutter, fork, or your fingertips, until a coarse sandy texture is achieved. Add the milk and ice water in dribbles until a shaggy dough is formed. Press the dough together into a mass, divide in two, and tightly wrap each half in plastic wrap, forming each into a rough 3″x5″ rectangle as you do. Refrigerate for at least 30 minutes, or until the jam is completely cooled.
3. On a generously floured surface, roll the first rectangle out about 1/8″ thick, to a size slightly larger than 9″ x 12″. Using a ruler, trim the edges and set them aside, along with the rectangle of rolled-out dough. Repeat with the second half of the dough, then cut both rectangles evenly into thirds lengthwise and width-wise, creating nine 3″x4″ rectangles from each half of dough.
4. Preheat the oven to 350°F and line a rimless baking sheet with parchment. Lay nine of the rectangles on the baking sheet, leaving a little space in between. Spoon 2 tablespoons of strawberry jam into the center of each rectangle, then brush the outer inch edges with milk. Lay their partner rectangle of dough on top, press gently with your fingers to seal, then gently crimp with a fork to reinforce the seal. Brush the tops with milk and bake until golden brown, 25-30 minutes.
5. Allow to cool completely, then prepare the icing by mixing the powdered sugar with milk (you can add some of the syrup from the jam to make it pink, if you like). Be sure to stir out all the lumps! The texture should be as thick as sweetened condensed milk. Drizzle or spread the icing on top of the cooled pastries, then add sprinkles or sparkling sugar, if desired.