Pour sugar over strawberries in a medium sized bowl and stir to combine. Cover and refrigerate for 2 hours or even overnight.
Place a small pot underneath a strainer and pour the strawberries with juice into the strainer.
Remove about 3 tablespoons of the juice and place in a very small bowl or cup. Add cornstarch and stir until smooth to create a slurry. Add slurry back into strawberry juices.
Cook strawberry juice over medium to high heat until juice thickens. Remove from heat and cool. Add strawberries back into cooled juice and store in a sealed container in the refrigerator until served.
