2) Line a baking sheet with parchment paper. Stir together the cornstarch and 1 1/2 tablespoons cold water in a small bowl.
3) Combine apples, pears and lemon juice in a large saucepan and add sugar. Cook over medium heat, stirring occasionally, until juices are released, about 10 minutes. Add cornstarch mixture; bring to a boil, stirring often. Remove from heat, add vanilla and let cool to room temperature.
4) Roll out pastry on a lightly floured surface to an 18 x 15" rectangle. Using a sharp knife, cut dough into 8 equal rectangles.
5) Place 1 pastry rectangle on a work surface at a time and brush edges with egg wash. Scoop about 3 tablespoons fruit mixture onto one side; fold dough over filling so the short ends meet, forming a packet. Crimp edges with a fork to seal. Using a sharp knife cut a few slits in top of pie to vent. Place on prepared baking sheet; repeat with remaining dough and filling.
6) Brush tops with egg wash, then sprinkle with raw sugar. Chill for 30 minutes. Bake pastries until tops and bottoms are golden brown, 30-40 minutes. Let cool for 10 minutes on baking sheet. Dust pies with powdered sugar if desired and serve with whipped cream or ice cream.
Wash and dry the fruit. Using a vegetable peeler, remove the zest from the fruit. Cut the zest strips into a fine confetti. Combine the zest in a pot with 6 cups of cold water. Bring to a boil, reduce temperature to medium high and simmer for half an hour.
While the zest cooks, cut the white pith away from the fruit and separate the fruit from the membranes. Collect the interior fruit in a large measuring cup and set the membranes and any seeds aside.
When all the fruit has been broken down, bundle the reserved pith and seeds into a length of cheesecloth, tying the cloth well so that no seeds can escape.
Drain the zest, reserving the cooking liquid.
In a large stainless steel or enameled cast iron pot, combine zest, citrus fruit, 4 cups of zest cooking liquid, sugar and the cheesecloth bundle. Bring to a boil and cook vigorously until the mixture reaches 220 degrees (this takes between 30-40 minutes). When the marmalade sustains 220 degrees for one minute, remove the pot from the heat. Stir for about a minute off the heat, to help the zest bits become evenly spread throughout the preserve.
Fill prepared jars, wipe rims, apply lids and screw rings. Lower into a prepared boiling water bath and process for five minutes at a gentle boil (do not start counting time until the pot has achieved a boil).
When time is up, remove jars from the pot and let them cool completely. When they are cool to the touch, check the seals by pushing down on the top of the lid. Lack of movement means a good seal.