Maple syrup, whipped cream and fresh blueberries for garnish (all optional)
In a bowl, combine the brown sugar, cinnamon and butter, mixing well. Sprinkle one-third of the mixture evenly over the bottom of your prepared slow cooker stoneware. Cover with 6 bread slices. Sprinkle with another third of the sugar mixture and scatter berries over top. Top with remaining bread slices. Sprinkle with remaining sugar mixture.
In a large bowl, beat the eggs, milk, vanilla and salt. Pour the mixture evenly into the slow cooker. Press down lightly on bread slices. Cover and refrigerate overnight.
Place the stoneware into the slow cooker. Cover and cook on Low for 3 to 4 hours or until eggs are set and browned.
Serve with maple syrup, a dollop of whipped cream and blueberries, if desired.