1. Preheat oven to 350°F.
2. To prepare graham cracker crumble: combine graham cracker crumbs, melted butter and sugar in a bowl and mix to blend. Press the crumb mixture into the bottom of a small pie pan. Bake for 4 to 5 minutes, or until lightly browned. Cool; crumble into pieces.
3. To prepare chocolate ganache: Bring heavy cream to a simmer, stirring occasionally; pour over chocolate chips and let stand for 10 minutes. Whisk until smooth and creamy. If making ahead, chocolate ganache can be reheated in microwave in 10 second increments until melted, stirring frequently.
4. To prepare French toast: combine eggs, half and half, and vanilla in a shallow bowl and whisk to blend. Melt butter in a large heavy skillet over medium heat. Dip bread slices in egg mixture; drain excess and griddle on each side for 3 minutes, or until golden.
5. Preheat broiler. Place marshmallows on baking sheet; run under broiler until puffy and lightly toasted.
6. To assemble each s’mores French toast sandwich: arrange 6 toasted marshmallows on 1 slice of warm French toast; drizzle warm chocolate ganache over marshmallows. Top with 1 slice of French toast, forming a sandwich. Top, as needed, with a drizzle of chocolate ganache, blueberries, maple syrup and graham cracker crumbles. Cut sandwich in half. Repeat with remaining s’mores French toast components to make additional sandwiches.