Make the BatterIn a medium bowl, whisk the eggs and milk until fully combined. Add the flour and salt and whisk until smooth. Let the batter rest at room temperature for 20–30 minutes.
Cook the CrespelleHeat a 8 inch nonstick pan over medium‑low heat. Lightly wipe the surface with oil, then remove any excess.Pour about ¼ cup of batter into the pan and swirl immediately to create a very thin crespella. Cook for 30–40 seconds until set, then flip and cook for another 10–15 seconds.Transfer to a plate and repeat with the remaining batter. Stack the crespelle and keep them covered.
AssembleLay one crespella flat and sprinkle lightly with Parmigiano Reggiano. Fold into quarters or roll gently. Place 2–3 crespelle into each warmed bowl.
Serve in BrodoBring the beef bone broth to a gentle boil and taste for salt. Ladle the very hot broth over the crespelle just before serving. Serve immediately.