Preheat oven to 200°C | 390°F.Lightly grease a 28x23-cm | 9x11-inch casserole dish with cooking oil spray or a light coating of butter. Place the bread slices into the dish, and arrange the dates all around, under and in between the bread slices.Whisk together the eggs, milk, brown sugar, vanilla, cinnamon (if using), and salt until frothy and well combined. Pour the egg wash over the bread. Press the bread lightly into the egg wash to evenly coat.Bake in preheated oven util cooked through and golden on top (about 40-45 minutes).While the french toast is in the oven, prepare sauce:Combine the sugar and butter in a medium sized saucepan on low heat. Occasionally stir until the brown sugar has melted through the butter, When the mixture is hot and steaming (after about 2 minutes), gradually add the cream in small amounts, stirring in between each addition, until all of the cream is in the pan. Add in the dates and allow the sauce to bubble up and froth, while still occasionally stirring. After about 8 minutes the sauce should be thickened and the dates will be soft. Take off heat and allow to cool slightly. Pour in 1 tablespoon of boiling water at a time (whisking after each addition), until reaching your desired consistency.Serve a slice with a drizzle of butterscotch and softened date pieces!