Whisk the sugar, rum, vanilla, orange zest and 1/4 teaspoon salt in a large bowl until the sugar dissolves. Add the cherries and cornstarch and toss; set aside until juicy, about 30 minutes.
Line a baking sheet with foil and coat with cooking spray. Place six 5-to-6-inch ceramic tart dishes on the prepared pan. Add 3/4 cup cherries to each dish using a slotted spoon; top each with 1 tablespoon butter and 2 teaspoons chocolate. Transfer the remaining cherry mixture to a saucepan; add 1/2 cup water and simmer over medium heat, stirring occasionally, until thickened, 5 to 7 minutes. Divide among the dishes; cool completely.
Dust a surface with flour. Using a paring knife, cut out 6 circles from the piecrust, 1/2 inch bigger than the tart dishes (use the dishes as a guide). Place on another baking sheet; chill until ready to bake.
Position a rack in the lower third of the oven and preheat to 375 degrees F. Top each dish with a piece of dough, pressing the edge against the dish to seal; pierce several times with a knife. Bake 45 minutes, then brush each pie with heavy cream and sprinkle with sugar. Continue baking until golden, about 15 more minutes. Serve with ice cream.
Photograph by Con Poulos
"Sweet: Our Best Cupcakes, Cookies, Candy and More" by The Editors of Food Network Magazine. Copyright Food Network Magazine, LLC 2014. Clarkson Potter/Publishers. All rights reserved.