Preheat the oven to 350F/177C convection (or 325F/162C conventional) and grease and line an 8" square pan with baking spray and parchment paper. Use binder clips to secure the paper to the baking pan.
Crush the graham crackers and combine them with the flour, baking powder, salt and cinnamon. Set the dry ingredients aside.
1 cup graham cracker flour, 3/4 cups all-purpose flour, 1 tsp baking powder, 1/2 tsp salt, 1/4 tsp pinch cinnamon
Beat together the egg and brown sugar, until they're pale and fluffy. Add the butter, Eagle Brand sweetened condensed milk and vanilla extract. The butter will be chunky- keep beating until it becomes smooth and fluffy.
1 large egg, 1/4 cup light brown sugar, 1/2 cup butter, 1/2 cup (4oz) Eagle Brand sweetened condensed milk, 1 tsp vanilla extract
Fold in the dry ingredients just until they're combined. Spread the blondie into the prepared pan and bake it for 17 minutes, then allow them to cool in the pan.
Chocolate Ganache
Melt together the Eagle Brand sweetened condensed milk and dark chocolate (in the microwave for two 20 second intervals or over a double boiler).
3/4 cup (6oz) sweetened condensed milk, 3/4 cup dark chocolate morsels
Stir until the mixture is smooth and then spread it over the cooled blondies. Refrigerate until the chocolate is set.
Homemade Marshmallow Fluff
Combine the egg whites and granulated sugar in the bowl of a stand mixer. Place the stand mixer bowl over a small pot of simmering water, creating a double boiler. Whisk the egg whites and sugar over the heat until the sugar is fully dissolved and the egg whites are frothy.
2 large egg whites, 1/2 cup granulated sugar
Remove the bowl from the heat and place it in the stand mixer. Using the whisk attachment, beat the egg whites and sugar until soft peaks form. Add the vanilla and salt and continue to beat until stiff peaks form.
1 tsp vanilla extract, 1/4 tsp salt
Spread the meringue over the chocolate and use a kitchen torch to toast it.