In a medium sized bowl, whisk together flour, baking soda, baking powder and salt. Set aside.

In the large bowl of a standing mixer, cream butter and 1 cup sugar together until light and fluffy. Add egg and beat to combine. Add cream cheese, cream, and vanilla, and beat until combined. Add the flour mixture and beat on low speed until incorporated. Dump dough onto a large sheet of parchment or waxed paper on the counter. Wrapping parchment around dough (to avoid sticky fingers), form dough into a ball, and flatten into a disk. Refrigerate 1 hour, wrapped in parchment paper.

Meanwhile, sprinkle sugar and cornstarch over strawberries in a medium sized bowl. Set aside. Line 2 baking sheets with parchment (or waxed) paper and set aside.

After dough has chilled at least 1 hour, preheat oven to 375 degrees, then dampen a sheet of paper towel and lay it flat on the counter. Roll out the dough between two sheets of parchment (or waxed paper) on top of the damp paper towel (to prevent it from sliding around on the counter when rolling). Aim for about 1/8 inch thickness. Cut out circles using a large (5 inch) circular cookie cutter, or whatever else you have on hand. At this point I found it necessary to chill the dough, as it became a bit too sticky to work with; I transferred the parchment to a baking sheet and put the whole thing in the freezer for about 2 minutes. Using a metal spatula, lift the dough circles and transfer them to the parchment-lined baking sheets. Make a new ball from dough scraps, and repeat the rolling out and circle cutting.

Mash the strawberries slightly with a fork or a potato-masher. Spoon approximately 2 tablespoons of strawberries onto one half of each circle. Fold dough over filling and pinch to close. Brush each pie with egg white, and sprinkle with sugar. Use scissors to snip a couple of vents in each pie to prevent the steam from popping open the seams. Bake until golden brown, 20-25 minutes, rotating the pans once during baking if you have two in at the same time. Cool on a wire rack.