Add milk, flour, sugar, salt, melted and slightly cooled butter, vanilla and eggs to a high-powered blender. Blend on low speed until well combined, about 10-15 seconds.
Scrape sides and bottom of the blender if there's any flour sticking, and blend a few seconds longer. Cover and chill in the fridge for 1 hour (or overnight if desired).
Cut small squares of parchment to separate crepes. This is important so they don't all stick together after being cooked, and especially important if you are saving/storing crepes in the fridge for later.
Heat an 8-to-10-inch nonstick skillet over medium to medium-low heat. Remove the batter from the fridge and give it a quick stir. Place one square of parchment paper down on a large tray or platter. This is where you'll stack the crepes as they are cooked.
Lightly butter the skillet with melted butter and a pastry brush or paper towel dipped in the butter. Barely lift the pan off the heat and pour 1/4 cup crepe batter into the pan. Immediately, and working quickly, tilt and swirl the crepe pan in a circular motion to evenly coat the bottom of the pan with batter. Return skillet to the heat.
Cook until the crepe is golden brown on the bottom (1-2 minutes) and then use an offset spatula to lift an edge of the crepe. Gently grab that edge of the crepe and using your fingers and the spatula, flip the crepe to the other side. Cook until golden brown spots appear (another 1-2 minute on bottom) and then remove to the prepared plate/tray. Place a piece of parchment or wax paper on top of the crepe.
Repeat until all of the batter has been used. If crepes are cooking too quickly, reduce the temperature of the burner as needed, and alternatively increase the heat if they are taking longer than 1-2 minutes per side to cook.
TO SERVE: Soften Nutella in the microwave by transferring it to a microwave-safe bowl and microwaving for 15 seconds and then stirring. (Microwave another 15 seconds if needed). You don't want it too warm/melty, just so it can easily spread. Spread Nutella along the bottom half of the crepe. If desired, top with fresh, thinly sliced fruit. Fold crepes in half, and then half again to form triangles. Sprinkle with powdered sugar and add some whipped cream as desired. You can also add a drizzle of Nutella if desired. (Transfer Nutella to a plastic bag, seal without air, and cut off the tip with scissors. Pipe over the Nutella triangles.)
TOSTORE: Let cooked crepes cool completely and then transfer the crepes to a large plastic bag. Seal without any air and refrigerate up to 5 days.
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Notes
Nutritional information includes the crepe with 2 tablespoons of Nutella filling, but no additional fillings and no powdered sugar sprinkled on top.