Wash the berries and combine them with the maple syrup and lemon juice in a large soup pot.
Bring to a boil, then reduce heat and simmer the mixture for 30 minutes.
Let cool, then purée in a blender, and strain into a large bowl.
While the blueberries are cooking, place the lavender buds and the cream in a 2-cup, microwave-safe measuring cup.
Microwave on high for 1 minute, then let the lavender steep at room temperature for 10 minutes.
Add the buttermilk and chill. It will basically become crème fraîche.
When berries are cool, strain the cream mixture into the strained blueberries and mix well.
Chill for at least 4 hours prior to serving.