Preheat oven to 375 degrees. Line heavy cookie sheet with parchment paper.
Defrost one sheet of puff pastry, per package instructions.
In a small saucepan mix together the ½ cup sugar and cornstarch, add the 3 tablespoons juice and drained cherries, and mix gently. Bring just to a boil over medium heat stirring constantly. Remove from heat and set aside.
After defrosting, place pastry sheet on a floured surface and gently unfold. Using a pizza cutter cut into four equal pieces. Taking one piece at a time, using a rolling pin, roll to a thin square, about 7”-8”.
Place one-fourth of the cherries in the middle of the square. Moisten two edges with egg wash and fold into a triangle and seal by pressing with a fork or folding edges over and crimp like a piecrust. Place on the parchment lined cookie sheet.
Brush each with egg wash and sprinkle with remaining 1 teaspoon sugar.
Bake at 375 degrees for 20 to 23 minutes, until turnovers are golden brown.