Dissolve gelatin in cold water.
Add blueberries + water + sugar in a saucepan. Let it simmer for 10 minutes until it slightly thickens. Strain the syrup through a sieve. Reserve the blueberries for toppings.
Meanwhile, add heavy cream + sugar to a saucepan and bring it to a simmer. (Do not let it boil). Turn off the heat and add vanilla and gelatin. Mix until gelatin dissolves.
Strain the mixture through a sieve to get rid of any undissolved gelatin. Add 1/2 cup of blueberry syrup and mix well.
Pour into 8-10 mini dessert cups leaving at least 1/2 an inch on the top. Let it sit on the kitchen counter to cool completely, about 20 minutes.
Refrigerate for an hour or two for it to set well. After an hour top the dessert cups with remaining syrup and refrigerate again. (You can add only the syrup or a mix of reserved blueberries along with syrup).