Measure ingredients: spoon and level 2 cups all-purpose flour; have 2-1/2 cups whole milk, 1/4 cup granulated sugar, 1/4 teaspoon fine sea salt (or a heaping 1/8 teaspoon table salt), 4 tablespoons unsalted butter melted and slightly cooled, 2 teaspoons vanilla extract, and 4 large eggs ready.
Add the milk, flour, sugar, salt, melted and slightly cooled butter, vanilla, and eggs to a high-powered blender.
Blend on low speed until the batter is smooth and well combined, about 10–15 seconds. Scrape the sides and bottom of the blender and blend a few seconds more if any flour remains.
Cover the blender and chill the batter in the refrigerator for at least 1 hour (or overnight if desired).
While the batter chills, cut small squares of parchment paper to separate cooked crepes on the stack tray.
When ready to cook, heat an 8– to 10-inch nonstick skillet over medium to medium-low heat. Remove batter from the fridge and give it a quick stir to recombine.
Place one parchment square on a large tray or platter where you will stack the finished crepes.
Lightly butter the skillet by brushing it with a small amount of the melted butter using a pastry brush or a paper towel dipped in the butter.
Barely lift the pan off the heat, pour 1/4 cup crepe batter into the center of the pan, then immediately return the pan to the heat and quickly tilt and swirl the pan in a circular motion to evenly coat the bottom with a thin layer of batter.
Cook until the crepe is golden brown on the bottom, about 1–2 minutes. Use an offset or thin spatula to lift an edge, slide the spatula under the crepe, and flip it to the other side. Cook until golden brown spots appear, about another 1–2 minutes.
Transfer the cooked crepe to the prepared tray and place a parchment square on top of it. Repeat steps 8–10, stacking crepes separated by parchment squares, until all the batter is used. Adjust the heat lower if crepes are cooking too quickly, or higher if they are taking longer than 1–2 minutes per side.
Soften Nutella: put the desired amount of Nutella in a microwave-safe bowl and microwave for 15 seconds, then stir. Repeat another 15 seconds if needed. You want it soft enough to spread but not very hot or runny.
To assemble each crepe, spread a thin layer of softened Nutella along the bottom half of a crepe. Top with fresh sliced fruit such as bananas and/or strawberries if desired.
Fold the crepe in half, then fold in half again to form a triangle.
If desired, sprinkle with powdered sugar and/or serve with whipped cream. To drizzle extra Nutella, transfer softened Nutella to a plastic bag, remove excess air and seal, cut a small tip from a corner with scissors, and pipe over the crepe triangles.