In a bowl, combine eggs, milk, sugar, melted butter, and flour. Mix the batter and strain it to remove any lumps. To make crepes quickly and evenly, you can spread the batter in a flat plate with high edges and press the crepe pan directly onto the batter. Then flip it over to finish cooking on the other side. Prepare the cream for filling the crepes as well: In a bowl, mix mascarpone, heavy cream, sugar, and vanilla. Fill the crepes by spreading the cream, rolling them up tightly, and if you like, drizzle with honey and sprinkle with chopped hazelnuts!