In a large bowl, add the flour and salt and whisk to combine. Add the cubed butter and use your fingers to smash the butter and rub it into the flour. Rub between your hands to create sheets of butter that is coated with flour. Continue rubbing the butter into the flour until all of it is flattened and the pieces are about the size of quarters. The mixture should look like coarse cornmeal.

Add about 4 tablespoons of water and fold it in with a danish dough whisk or a wooden spoon. Add more water, one tablespoon at a time until it appears shaggy. You may not need all of the water.

Dump the dough onto a floured work surface or countertop. Press the dough into a rectangle. Lightly flour the top and use a rolling pin to roll it out to about 8×10 inches. Use a bench scraper to lift one side of the dough and fold it up and over ⅓ of the dough, onto itself in a letter fold. Lift the other side to complete the letter fold. Repeat the letter fold two more times. This is the process that will create the layers in the dough.

Divide the dough into two pieces and wrap each piece in plastic wrap or reusable wax food wraps. Chill the dough for at least 30 minutes. The dough can be made in advance and refrigerated for up to 1 week or frozen for up to 1 month.

In a medium pot, mix together the strawberries, rhubarb, sugar, cornstarch, jam, salt, zest, and vanilla. Over medium-high heat, bring the filling to a boil. Then lower the heat and let the filling simmer until the fruit is soft and the liquid has reduced for about 20 minutes. Transfer the filling to a bowl and refrigerate until cold.

Line two baking sheets with parchment paper. Remove one of the pie dough discs from the refrigerator and let it warm up enough to be pliable but still cool. Mix the egg and the water together in a small bowl. Take out a pastry brush and a fork.

On a well-floured board, roll out the dough to about ⅛ inch thickness. Using a knife or a pizza cutter, cut out as many dough squares as you can. I cut mine to about 3 x 3 inch squares. Gather the dough scraps up again into a disc and roll it out one more time. Cut out some more dough squares.

Measure out 1 tablespoon of the filling and carefully place it in the middle of one of the dough squares. Using your pastry brush, brush the edges with egg wash. Place a second dough square on top and seal the edges. Take your fork and press it down along the edge to crimp it. Move the pie to the lined baking sheets. Repeat until you have used up all of the dough squares.

While you are finishing up the first set of hand pies, take the second disc of dough out of the refrigerator and let it warm up. Repeat the whole process with the second piece of dough. At this point, you can move the baking sheets to the freezer and freeze the pies until solid, and then put them in a sealed bag. Pies can be frozen, well wrapped and sealed, for up to 3 months. Bake them from frozen, adding 1-2 minutes to the baking time.

If not freezing, transfer the baking sheets to the refrigerator to rest for 30 minutes. Preheat oven to 375F.

Brush the tops with egg wash, sprinkle liberally with coarse sugar, and cut a small hole or two in the top to vent the pies. Bake the hand pies for 18-20 minutes, or until they are golden brown and the filling is bubbling up through the vents. Enjoy warm or at room temperature with some vanilla ice cream.

The pies are best on the day they’re baked. Store the pies at room temperature in an air-tight container for 2 days or in the refrigerator for up to a week. Reheat the pies in a 350°F oven.