This method works for ANY kind of frozen berry. And if you don’t want to use chia seeds to thicken (and add Omega benefits) substitute 1 tablespoon of cornstarch dissolved in 1/4 cup of water.
In a medium sized sauce pan, combine berries, water or juice, chia seeds (or cornstarch, see note above) and sugar plus vanilla if using.
Bring to a boil over medium-high heat. Stir often to break up frozen berries.
Serve when thick and bubbly, about 5-8 minutes.