Make the filling: In a sauté pan on medium heat add avocado oil. Once warm, add kale and onion. Sauté until onion has caramelized and kale has wilted. Remove from heat and set aside.
Make the crepes: In a large bowl whisk together flour, salt, and sugar. In another bowl, whisk together eggs, heavy cream, water and butter. Create a small well in the flour mixture and slowly pour in liquid, whisking continuously until thoroughly combined. Let mixture stand for 5 minutes.
Preheat a large sauté pan, frying pan or crepe pan on medium heat. Lightly spray with oil. Pour 1/3 cup of batter into the center of pan and quickly tilt pan around to allow batter to run and create a large, thin crepe. Once the edges are set, using a spatula carefully flip crepe and cook for another 30 seconds. Slide crepe off of pan and onto a plate. Repeat until all crepes are made.
Build crepes: sprinkle crepe with a bit of brie and top with a few scoops of kale and caramelized onion mixture then roll up and plate. Repeat until all crepes are filled and plated.