Combine all ingredients in a large bowl, mixing well until incorporated. Keep refrigerated until ready to use.
Fold all ingredients together in a bowl until well incorporated but not completely smooth.
Combine all ingredients in a saucepan over medium-high heat. Stir until sugar dissolves. Bring to a boil and let reduce by 1/3.
Preheat oven to 350 degrees F.
Heat a large saute pan and then add butter. Dredge the bread in the batter and place in the pan. Cook until golden brown on both sides, approximately 2 minutes. Remove from pan and let cool. Divide filling between 2 pieces of the bread top with the remaining 2 pieces of bread. Transfer French toast to oven and bake for 8 minutes.
Cut each French toast in half and serve with the cinnamon syrup and, if desired, a large scoop of vanilla ice cream and fresh berries.