2 cups frozen, unsweetened strawberries
1/4 cup sugar
1 tablespoon cornstarch
approximately 2 additional tablespoons sugar
Measure frozen strawberries into a strainer set over a medium saucepan and sprinkle with 1/4 cup sugar. Leave to thaw, stirring and pressing into the strainer occasionally. Dump the drained, thawed berries into a blender and puree until smooth. Leave them in the blender. Leave the strawberry juice in the saucepan.
Mix the cornstarch and 2 tablespoons of sugar together and whisk into the strawberry juice. Bring to a boil over medium heat, stirring constantly. As soon as the mixture is bubbly and thick, remove it from the heat and cool several minutes. Test for sweetening and add more sugar if needed. Pour on top of the pureed strawberries that are still hanging out in the blender, and pulse several times just to mix. You're not trying to whip this into submission, just to bring the thickened juice and source strawberries into one happy saucy marriage.
Pour into a covered container and chill until needed. Makes 2 cups (ish).
Source: https://guiltychocoholicmama.blogspot.com/2018/06/seriously-strawberry-sauce.html