Preheat oven to 375 degrees.
In a large bowl, combine rhubarb, strawberries, sugar, tapioca and orange juice. Mix well. Let stand 15 minutes.
Spoon mixture into 6 one cup ramekin dishes. Place on parchment lined rimmed baking sheet.
Make pie dough:
Stir together flour, salt and sugar in the bowl of a food processor. Add the cubed butter and pulse for a few seconds until mixture resembles coarse crumbs with a few larger pieces. Sprinkle the water over the flour mixture and process until the dough comes together.
Place the dough on a lightly floured surface and roll to about 1/8 inch thick. Cut out 6 rounds of dough, about 1/2 inch larger than the top of the ramekin. Using a small decorative cookie cutter, cut a vent into the middle of each round. Place the dough rounds on top of the filled ramekin dishes, pressing the edges down over the rim. Cut a vent in the middle of the dough at this point if you don't have a small decorative cookie cutter.
Brush dough with egg wash and sprinkle with turbinado sugar, if desired.
Bake for 35 minutes until lightly browned and the fruit is bubbly.
Let cool 10 minutes. Serve with vanilla ice cream, if desired.