Method:

Prepare a medium sized baking dish or casserole and preheat the oven to 180°C
Mix half the sugar with half of cinnamon. Sprinkle half the cinnamon sugar over the bottom of the baking dish. Place the sliced bread on a chopping board and spread one slice of bread with the chocolate hazelnut spread and sandwich with another slice of bread. Repeat this process until the loaf is finished. In a large bowl, whisk together the eggs, milk, vanilla and some salt. Submerge the sandwiches into the egg mixture and allow the bread to sit in the mixture for a minute to soak up the eggs. Arrange the sandwiches in the baking dish and pour over the remaining egg mixture. Sprinkle over the remaining cinnamon sugar. Cover with plastic wrap and refrigerate for 20 minutes. In a bowl, combined the remaining sugar, remaining cinnamon, flour and butter. Spread this mixture over the sandwiches. Cover with foil and bake for 20 minutes, remove the foil bake for a further 20 minutes until the toast is deeply golden. Mix the topping ingredients together. Serve the French toast warm finished off with the yogurt topping.