Place the raspberries and honey or agave in a saucepan over low to medium heat, stirring to combine and smashing the raspberries with the back of a spoon.
Bring the mixture to a simmer.
Whisk the cornstarch and water in a small bowl.
Add the cornstarch mixture to the raspberries and stir until the sauce thickens (about 2 minutes).
Cool and serve over yogurt, ice cream, pancakes and more!