Add apple slices, brown sugar and 4 tablespoons of butter to a medium saucepan and cook over medium-high heat until sugar has dissolved and butter has melted. Add ¼ teaspoon vanilla and ½ teaspoon of cinnamon. Reduce heat to simmer. Cook for 6 minutes, remove from heat and allow to cool. 

In a large bowl, whisk together eggs, milk, remaining ¼ teaspoon vanilla and remaining ½ teaspoon cinnamon. Add flour and whisk until smooth. 

Submerge each slice of bread in egg mixture, one at a time. Shake excess liquid off each slice. 

Heat a non-stick skillet over medium heat. Melt remaining 1 tablespoon butter in hot skillet. Cook French toast for 2 minutes or until lightly browned. Flip and continue cooking until the second side is lightly browned.

Stack two slices on each plate. Generously top with cooked apple-cinnamon mixture. Drizzle with caramel sauce and enjoy.