How to Make It
Whisk together eggs, broth, fish sauce, and salt in a bowl. Divide celery leaves and scallion evenly between 2 (12-ounce) bowls. Pour egg mixture through a fine wire-mesh strainer evenly into bowls. Wrap each bowl in plastic wrap (use rubber bands to secure plastic if it doesn’t adhere to sides).
Place bowls in a large steamer basket set over a large saucepan of simmering water. Cover and cook until custards are just set, 15 to 18 minutes.
Carefully remove bowls from steamer basket; remove and discard plastic wrap. Let custards stand 5 minutes.
Meanwhile, place shrimp in a single layer in steamer basket. Cover and cook until opaque and cooked through, about 1 minute.
Top custards evenly with shrimp; garnish with celery leaves and scallion.