Prepare your mise en place.
Combine the cherries, sugar, and kirschwasser in a medium saucepan over medium heat. Bring to a boil, stirring occasionally with a wooden spoon.
Place the cornstarch in a small bowl and add just enough cold water to dissolve it.
Stirring the cherries constantly, add about half of the cornstarch slurry to the cherries. Continuing to stir