Place strawberries, water and sugar in medium saucepan and cook on medium/high.
Cook strawberries, stirring occasionally for 5-7 minutes or until strawberries start to soften.
Take large glass, potato masher and crush strawberries. If using a blender, place strawberries in a blend and blend, then return to pan. See note below.
Bring strawberries to a boil.
Meanwhile, take cornstarch and place in a small cup. Add ¼ cup water to the cornstarch and stir.
Once strawberries are boiling, reduce heat to medium/low and add cornstarch mixture to the strawberries, stirring frequently.
Turn off heat when strawberry mixture is thickened, about 3 minutes.
Let cool until desired temperature and serve.
Notes
Be sure to take care when mashing berries, they will be hot. You can skip this step if desired, the sauce will still be delicious.