Combine Crepe ingredients in a blender or bullet blender and blend until batter is smooth and free from lumps (about 2 minutes). Scrape the sides down with a spatula and the inside of the base, and blend again for a further minute to ensure all flour has been blended.Pour about ¼ cup batter onto the centre of a nonstick pan lightly greased with butter, while swirling the pan to evenly cover the base and create a thin crepe. When golden and crepe begins to pull away from the sides of the pan, flip (I use my fingers to flip them).Remove when cooked through (about 1-2 minutes per side), and repeat with remaining batter. Fill each crepe with Nutella and roasted marshmallows (see below) and fold over. Top with graham cracker crumbs.Cover a baking tray with parchment/baking paper, and place marshmallows on the tray in a single layer. Place into a preheated oven with grill/broil settings on medium heat and oven shelf in the middle or upper part of the oven (not to close to the top of the oven, or they can burn.)Keep an eye of your marshmallows, and after about 2 minutes or when golden on top - melted and spread out, remove them and immediately spoon them onto your crepes.