Preheat oven at 375 F (190 C). Crush granola bars in their packages or in the blender. Mix flour with crushed granola bars, icing sugar and butter until you obtain chunks. Spread on an ungreased cooking plate and bake for 12 to 15 minutes, until crumble is golden. As soon as they come out of the oven, split with a wooden spoon.
Pour balsamic vinegar and maple syrup in a microwaveable plate and heat for one minute at maxium power. The mix should start boiling without becoming too gummy; it will get harder when it cools.
In a microwaveable bowl, mix frozen blueberries with white sugar and if wanted, lavender.
Microwave for two minutes at maximum power. Let cool.
With an electric batter, whip cream until ferm. Add to mixture.
Prepare 8 parfait glasses. In each of them, put 30 ml (2 tablespoons) bluberry mix. Cover with 60 ml (1/4 cup) crumble and cover with 30 to 45 ml (2 to 3 tablespoons) cream. Garnism with 10 ml (2 teaspoons) syrup.