Chill the bowl and whisk of a stand mixer in the freezer

Combine 1 cup of blueberries, lemon juice and zest, and sugar in a saucepan over medium heat and smash together with the back of a spoon or a potato masher

When mixture reaches a simmer, continue to cook, stirring often, until sort of thick and syrupy

Remove from heat, transfer to the bowl of a food processor, and cool completely

When blueberry mixture is cooled, add the sour cream and cream cheese to the food processor and puree with blueberries until smooth

Add heavy cream to the chilled bowl of a stand mixer, attach whisk, and beat on medium high until soft peaks form.

Fold the whipped cream into the berry mixture until well combined

Transfer the mousse to a zip top bag and cut a small piece of the corner completely off

Pipe mousse into small dessert cups or shooter glasses, cover and chill for at least an hour or overnight

Garnish with blueberries and chopped pistachios, if desired