Whisk the flour, brown sugar, baking powder, cinnamon and salt together in a large mixing bowl. Whisk the buttermilk, vanilla and egg yolks together thoroughly in another bowl. Pour those wet ingredients into the dry ingredients and whisk it all together until it is a smooth and really thick batter. Take the egg whites and use a hand mixer to whip them up until they form stiff peaks and are like fluffy clouds. Use a spatula to gently fold the egg whites and blueberries into the batter. Cover the bowl and refrigerate the batter overnight to let it rest.

In the morning, pre-heat an electric griddle to 350 or a griddle pan over medium high heat. Grease the griddle with the butter. Cook off the batter in batches, making whatever sized pancakes you desire. They take about 4 minutes on each side to get puffy and golden. Serve them immediately as you cook them with syrup, extra blueberries and a pat of butter on top! Enjoy!