Roll out the pie crusts onto a sheet of parchment paper or a lightly floured counter top. Use a 4 inch or larger round cookie cutter to cut out 12 mini pie crusts. Reserve the scrapes to reroll for the lattice in later steps.

Gently press each pie crust into the prepared muffin tin. Set aside.

In a large bowl, combine the rhubarb, strawberries, sugar, brown sugar, corn starch, lemon zest, vanilla and salt. Gently toss to combine.

Using a large spoon, carefully scoop out the filling and place into each prepared pie crust. Fill until the fruit reaches the top of each pie crust. The liquid can be divided and filled in around the fruit pieces. Set aside.

Use a sharp knife or pizza cutter to cut the remaining pie crust into ¼ inch size strips.

Lay two strips on top of each pie crust and then lay another two strips perpendicular to the first two. Weave the strips to create a simple lattice on top of each mini pie. Repeat until all mini pies are assembled. Trim off the excess strip pieces so that they are even to the top of the muffin tin and gently press to connect with the bottom pie crust.

Combine the egg and tablespoon of water in a small bowl.

Use a pastry brush to coat the lattice on top of each mini pie.

Sprinkle with the turbinado sugar.

Bake in the preheated oven for 23-25 minutes or until the filling is bubbly and the crust is golden brown.

Allow to cool slightly before gently removing from the pan. Use a butter knife to help release along the sides of the pie crust. Remove the pies while still slightly warm.