Step 1

If using fresh berries, wash the berries in cold water and let drain.

Step 2

Put the berries into a large bowl with the sliced plums and gently toss the fruit with 1/2 cup of the sugar and the lemon juice. Pour the fruit into a colander and set the colander over the bowl so that it catches all the juice. If using frozen berries, there is no need to thaw. The berries will thaw as they rest in the colander.

Step 3

Let the berries rest in the colandar at room temperature for 3 hours. If you think about it, gently stir the fruit in the colander every now and then to encourage as much juice as possible to drip down into the bowl. (If you forget, or are unable to stir the fruit, don't worry about it. It'll be fine.)

Step 4

Preheat the oven to 400° F (204° C).

Step 5

Remove the colander with the fruit in it from the bowl and pour the fruit juice that's collected in the bowl into a medium size saucepan. Dump the fruit into the bowl and set aside.

Step 6

Using a spice grinder or food processor, grind the tapioca into a powder. (*See note) Add the ground tapioca, remaining sugar, cornstarch, salt, honey, and lemon zest to the fruit juice in the saucepan. Whisk vigorously to combine and set it over medium-high heat.

Step 7

Cook the fruit juice mixture, stirring constantly, until the mixture comes to a boil. Boil, stirring constantly, for 5 minutes, until it's thickened to the consistency of gravy (*see note). Remove from the heat and stir in the vanilla.

Step 8

Pour the fruit juice mixture over the fruit. Toss gently to combine and set aside while you roll out the pie crust.

Step 9

Remove the pie dough from the refrigerator. On a floured surface, roll out a portion of the dough to a 12-inch circle that’s about ⅛-inch thick. Using a large spatula, gently loosen the dough from the work top, fold it in half and then fold it in half again. It will form a triangle shape. Lift the crust and place it in a pie plate with the point of the triangle in the center of the plate. Gently unfold the dough in the pan and press into the corners gently. Leave any dough that overlaps the edges of the plate in place.

Step 10

Spread 1/2 cup of fruit jam or preserves in an even layer over the bottom of the pie crust.

Step 11

Roll another portion of the dough into a large circle, about 18 inches. With a pizza wheel, fluted pizza wheel, or paring knife, cut the disk into 1 or 2-inch wide strips.

Step 12

Pour the fruit filling into the bottom crust, smoothing it into an even layer.

Step 13

Starting in the center of the pie, lay half the strips across the top of the filling in one direction. Lay the remaining strips perpendicular to the first, weaving them into the first strips to form a lattice pattern. Trim the edges of the strips so that they are even with the edge of the bottom crust.

Step 14

Fold the edges under, forming a rim around the pie that is a bit higher than the pie plate. With one hand on the inside of the edge and one hand on the outside, use the index finger of your inside hand to push the dough between the thumb and index finger of your other hand to form a U or a V shape. Continue this crimping motion around the entire edge.

Step 15

In a small bowl, whisk the egg with 1 tbsp of cold water. Gently brush the egg wash over the top crust with a pastry brush and sprinkle evenly with 2-3 tablespoons of sugar.

Step 16

Put the pie on a foil covered baking sheet and place in the oven. Bake for 30 minutes. Reduce the oven temperature to 375° F (190° C) and bake for an additional 30-40 minutes. The pie is done when the crust is a deep golden brown and the filling in the center of the pie is bubbling.

Step 17

Remove from the oven and let cool completely before slicing.