Put the lavender in a small bowl and pour warm water on top. Mix together and let it steep for at least 30 minutes.
Strain the lavender from the water and pour the 3 tbsp of lavender infused water into a sauce pan. Pour the honey into the sauce pan and cook over medium high heat until bubbling. Reduce the heat and let the honey mixture reduce and simmer until thickened and no longer watery, about 7-10 minutes.
For the Galette
Preheat the oven to 375 degrees F or follow the instructions on the puff pastry or pie crust packaging.
Thinly slice the brie.
Unwrap the puff pastry sheet and place it onto a parchment lined baking sheet.
Begin to layer the brie slices in the middle of the dough, leaving 2-3 inches around the perimeter.
Place the blackberries on top and in between the brie slices.
Fold the edges of the dough slightly over the edges of the filling, encasing all the way around. Drizzle honey on top.
Place thyme on top of the galette and bake for 22-25 minutes, or according to the puff pastry package instructions.
If the galette isn't golden brown by 25 minutes of bake time, bump the heat to 400 degrees and cook an additional 5-7 minutes.
Remove the galette from the heat and drizzle honey lavender on top. If you don't like lavender, drizzle with regular honey.