Preheat oven to 425°F
Line a baking sheet with parchment paper.
In a mixing bowl, use the potato masher to lightly muddle the cherries, to break up their texture a little. Don't go overboard; you're not making mush.
Add sugar, almonds, and corn starch to the cherries, stir to mix, and set aside.
Remove the dough from the plastic wrap and place on the parchment paper. Using a rolling pin, roll out the dough until it's about ⅛" thick and circular.
Sprinkle your chocolate in the center of the dough, leaving about 2-3" from the edges bare.
Spoon the cherry mixture over the chocolate, again leaving the edges bare.
Gently fold the edges in over the cherries, working around the circle and pressing gently to seal.
Brush the edges of the dough with egg white, and sprinkle with remaining 1 Tbsp of brown sugar.
Cut up the remaining Tbsp of butter into flakes and sprinkle over the cherry mixture.
Bake for 25 minutes. When done, let cool before slicing to serve.