Boil blackberries, maple syrup and vodka, mashing berries gently as they cook until blackberries are broken down (about 5 minutes). Add lavender flowers (removing from stem if they are fresh) and boil for 1 minute. Remove from heat.
Optional: if time permits allow to steep for at least 1 hour and up to 2 days in fridge.
To serve: pour 1 tablespoon blackberry sauce into a champagne flute, add a stem of fresh lavender and top with chilled champagne.