Peel and slice two medium sized onions and add to a medium bowl.
Over a medium flame, melt butter then add in the sliced onions.
Continue to let the onions sweet and cook down over a mediumt o medium low heat, stirring occasionally as to keep the onions from burning and sticking. The onions should have a sweet smell and be golden in color.
Once the onions are done cooking, take off the heat. Take a small slice of brie and spread it onto the crostini, then add a small scoop of onions. Top with thyme and serve.
Notes
Do NOT add the flour to the onions! I took the ingredient photo anticipating using the flour, and in my first test, the onions with the flour ruined the flavor of the dish. So, ignore the flour in the photo.Take your time with caramelizing the onions low and slow. You can stir occasionally so that the onions do not burn, so be sure to give yourself the full hour to let the onions cook down.Take the brie out of the fridge 15-20 minutes before you want to use it so that it softens up prior to adding to the crostini.