I remember when I was little making a cake with raspberry sauce at a friend's house. She gave me the recipe but I managed to lose it and when I wanted to make the sauce again (years later) I had to recreate the sauce through trial and error and finally got it just right. It's a delicious topping for any number of desserts, including chocolate cake, but should either be made just before it will be used or distributed onto the dessert almost immediately after being made even if it will not be served until later.
½ c. sugar
2 Tbsp. corn starch or tapioca starch
1 bag frozen raspberries
Thaw raspberries and drain juice into a measuring cup. Add enough water to make 1 cup. In medium saucepan, stir together sugar and corn starch, then whisk in the liquid and add the berries. Heat over medium, whisking constantly, until the mixture boils and begins to look translucent instead of cloudy. Strain to remove seeds and pulp.