3 tbsp erythritol, more to taste (I use this brand)
In a medium sauce pan, combine the water, mixed berries and lemon juice. Bring to a bowl over medium-high heat. Once you bring it to a boil, reduce the heat to low and let simmer until the berries pop and release their juices. Use a fork to mash up the berries into the liquid.
In a separate sauce pan, combine the coconut milk, vanilla extract, vanilla bean paste and erythritol. Whisk to combine. Bring to a boil and then reduce heat to low and let simmer. Stirring frequently, let the mixture simmer until it has started to thicken just a bit.
Combine the contents of both sauce pans and whisk until all ingredients are well incorporated. Let cool.