Cut the rhubarb and strawberries into a medium dice and add to a medium mixing bowl with next three ingredients. Allow to rest for about 15 minutes.
In the meantime, roll out your pie crusts and cut 6- 4 ½” diameter circles. Gently press into the small pie tins. With the remaining dough, you can cut a 4” circle to place over your pies or cut 1/8” strips to create a lattice top crust, directions below.
Using a ½ C measuring cup, scoop a heaping amount into each pie shell, gently place the 4” pie crust over the strawberry rhubarb mixture and crimp the edges all around, using a paring knife, cut 2 1/2” slits at the top of the pie crust to allow steam to escape.
Brush the egg and milk mixture over the pie crust and immediately sprinkle the coarse sugar over.
Place the pies onto a parchment lined baking sheet and bake for approximately 20 minutes. The fruit mixture will bubble, and the crusts will turn golden brown.
Pull from the oven and allow to cool for about 10 minutes, you can serve them out of the pie tins, if you wish to remove them from the tins you will need to do this while the pies are still warm. Using a paring knife, gently place it between the pie tin and the bottom pie crust to separate any of the fruit mixture that has spilled over, use an offset spatula to carefully lift the pie out as you tilt the tin to help it slide.