Working with one bag at a time and leaving it unsealed, knead the mixture through the bag by pressing with the heel of your hand to help the dough come together. Remove the dough from the bag and knead it lightly just until it is slightly stretchy when pulled. Flatten the dough into a disk, wrap it in plastic wrap and refrigerate for at least 45 minutes, preferably overnight.

In a medium bowl, combine 1/2 cup granulated sugar and zest from 1 medium orange by using your fingers to rub the orange zest into the granulated sugar. This will help release oils from the zest and fully infuse the sugar with orange flavor. Set aside.

Add 1 1/2 pounds trimmed and sliced rhubarb, 1/4 cup cornstarch, 2 tablespoons fresh squeezed orange juice. Toss to combine ingredients until the rhubarb is coated. Use the tip of a sharp knife to slice 1 vanilla bean pod lengthwise; use the tip of a knife to scrape the vanilla beans over the fruit mixture, and toss again to combine.

Take one of the dough disks and divide into four, even pieces. Roll out each piece into a circle slightly larger than your mini pie dish (if you're using a shallow mini pie dish, the circle should be 1 to 2-inches larger than the dish; if you're using a deep mini pie dish, the circle should be 3 to 4-inches larger than the dish). These will be the base and sides of your crust. Gently nestle each circle into its own pie plate, using your hands to gently press the dough against the sides and base of the plate.

After the pies have frozen, preheat the oven to 425 (F). Place a baking sheet on the center rack of the oven.