Prepare the filling: Whisk the cornstarch and water together until all the cornstarch has dissolved. Place the berries, sugar, cornstarch mixture, and lemon juice into a small saucepan over medium heat. Using a wooden spoon or rubber spatula, stir the mixture as it cooks. Break up some of the berries as you stir. Bring it to a simmer and allow to simmer for 3 minutes, stirring constantly. Remove pan from the heat and cool completely. T Make the dough: Whisk the flour, sugar, and salt together in a large bowl. Place the cold and cubed cannabis butter on top. Gently toss the flour and butter together with your hands. This step is only possible if the butter is very cold because if the butter is warm, you’ll end up with paste. At this point, the cannabis butter is still in large cubes/chunks. Begin adding the ice cold water 1 Tablespoon (15ml) at a time until dough forms 1 large scruffy looking clump in your bowl. Use your hands to toss the mixture together after you add each Tablespoon.As the dough begins to hydrate after about 4 Tablespoons (60ml) of water, you can start lightly squeezing or clumping the dough together with your hands to help bring it together. Pour the clump of dough out onto a lightly floured work surface. There will still be large chunks of butter at this point and that’s a good thing. Begin patting the dough down with lightly floured hands until it’s 3/4 – 1 inch thick, about a 5×8 inch rectangle. Fold the dough into thirds as if you were folding a business letter. Use your hands to gently flatten and smooth out any cracks in your dough. Wrap it up tightly in parchment paper, and place in the fridge for a minimum of TWO (2) hours. Take the dough out of the refrigerator to begin the “rolling and folding” process. If the dough chilled for longer than about 3 hours, it’s likely very stiff so let it rest for about 5 minutes before you begin rolling. Lightly flour a work surface. The dough gets sticky, so make sure you have more flour nearby as you roll and fold.Fold the rectangle into thirds again, as if it were a business letter. Then turn it clockwise and roll it out into a 6×12 inch, 1/2 inch thick rectangle again. Then, fold into thirds again. Turn it clockwise. You’ll repeat rolling and folding 4 more times for a total of 6 times. Tightly wrap and refridgerate just as you did before for minimum 15 minutes.
Take it out of the fridge and line two large baking sheets with parchment paper.
Take the dough out of the refrigerator to begin the shaping steps. Lightly flour a work surface. Using a rolling pin, roll dough into a BIG 12-inch square. Using a pizza cutter or sharp knife, cut into 9 x 4-inch squares. Put the squares on the baking sheet. Take the filling and place in the middle of each square. Then fold the corners up to make a triangle and using a fork, gently crimp all of the edges so it's closed. Yet again: refrigerate! Just 10 minutes this time. Don't skip this step!
Preheat the oven to 400F, and make the egg wash as they finish up chilling.
Egg Wash: Whisk the egg and milk together. using this mixture, brush each turnover. Cut 3 slits into the tops of each to allow steam to escape. If desired, sprinkle with coarse sugar.
Bake for 22-25 minutes or until golden brown on top and around the edges.
Remove baked turnovers from the oven. Cool for at least 5 minutes before icing/serving. Centers will be hot.