Instructions

1. Make the pie crust: In a large bowl, mix the flour and sea salt together. Cut the cold butter into the bowl in small pieces, aiming for about 1/2 TBS per piece. Use a pastry cutter or a fork to cut the butter into the flour until it is crumbly with pea-size pieces of butter. Whisk together the eggs and the ice cold water in a small bowl until evenly combined. Add about half of the egg mixture to the flour and use a fork to quickly mix, moistening as much of the flour as you can. Test to see if the dough will hold together when pressed. If not, continue stirring in a splash of the egg mixture at a time until the dough just barely holds together when gathered into a ball. Once the dough holds together, stop adding the liquid, form into a ball and wrap tightly in plastic wrap. Refrigerate the dough until thoroughly chilled, at least 30 minutes.
2. Prepare the filling: Add the sliced rhubarb, sliced strawberries, raspberries, vanilla, cinnamon, brown sugar, white sugar, and tapioca granules to a large bowl. Stir gently with a wooden spoon until all of the filling ingredients are fully mixed and the fruit is coated with sugar. Set the filling aside.
3. Make the pie: Preheat the oven to 400 degrees F. Prepare a flat work surface for rolling out the dough by putting a dusting of flour on the work surface and on a rolling pin. Divide the dough into two pieces – one that uses 2/3 of the dough and the other that uses 1/3 of the dough. Roll the larger pieces out into a large circle that is about 1/4 of an inch thick and 12 inches in diameter. Carefully transfer this piece of dough into a 9-inch pie plate. Very lightly press the dough into the pie plate so that it the dough is touching all of the sides of the pan. You should have at least a half inch of overhang on all sides.
4. Spoon the filling into the prepared pie crust, taking care to fill the pie evenly and remove as many air gaps as possible by spreading the fruit around. Roll the second piece of pie dough out into a circle and cut into strips that are about 1/2 inch wide. Arrange the strips in a lattice pattern on the top of the pie. You may need to adjust pieces of the filling as you work to get the lattice strips to lay flat. Once you are happy with the lattice, gently press the lattice pieces into the edges of the lower pie crust, then trim the crust, leaving just a little bit of overhang (the crust will shrink as it bakes – press the overhang under the rim of the pie pan if you want it to stay all the way to the edge).
5. Use a pastry brush to brush all of the exposed pie crust lightly with milk. Bake for 20 minutes at 400 degrees F, then lower the temperature to 350 degrees F and bake until crust is golden brown and filling is bubbly, an additional 60 minutes. Let cool completely, preferably overnight, before serving.