For the dough: In a large bowl, whisk together the flour, granulated sugar, and salt. Scatter the butter cubes over the flour. Using either a pastry blender or clean fingers, cut the butter into the flour until it is thoroughly coated and the biggest pieces are the size of small peas. In the center of the flour mixture, make a “well” and add the milk and egg to the center of the well. Gradually incorporate the flour mixture into the milk mixture. Knead until the dough comes together, adding more milk as needed.
For the filling: Drain the cherries, reserving 2 tablespoons of juice. In a large saucepan, combine the cherries and reserved juice, granulated sugar, and cornstarch. Bring the mixture to a boil over medium heat, stirring constantly. Reduce the heat and simmer until the juice begins to thicken, about 7 minutes. Stir in the butter and almond extract, and set aside to cool to lukewarm.
For the streusel: In a medium bowl, combine the brown sugar, granulated sugar, flour, oats, almonds, and butter. Using your hands or a pastry blender, work the ingredients together until the mixture resembles coarse crumbs. Refrigerate until ready to use.
For the egg wash: In a small bowl, beat the milk and egg together.
To assemble: Place the dough on a lightly floured surface, and roll it into a rectangle, about 12 x 16 inches. Using a pizza roller, cut the dough into twelve 3 x 4-inch pieces. Reroll scraps and cut out 4 more pieces of the same size, for a total of 16.
Brush the egg wash over the edges of 8 pieces of dough; these will form the bottom of each hand pie. Place a heaping tablespoon of filling into the center of each bottom piece, then top with a piece of the remaining dough. Use your fingertips to press firmly around each pocket of filling, sealing the dough on all sides. Press the tines of a fork around the edge of each hand pie. Lightly brush the tops of the hand pies with egg wash. Then gently press some streusel into the top of each.
Line a baking sheet with parchment paper. Gently place the hand pies on the baking sheet, about 3 inches apart. Prick the top of each pie 4 times with a fork, to allow the steam to escape during baking.
Preheat the oven to 350°F. Chill the hand pies for 30 minutes.
Bake the pies until light golden brown, about 30 minutes. Allow them to cool for 30 minutes before serving.