Make the egg salad

• Smoosh the hard boiled eggs in a bowl with a fork.
• Add the kewpie mayo and black pepper and mix until creamy.

Boil the potato

• Boil the potato in salted water until fork tender.

Cook the shallots and sausage meat

• Sauté the shallots in a pan until soft.
• Add the sausage meat and cook through, breaking it up.

Make the croquette filling

• Mash the drained potato in a bowl with the butter, salt and black pepper.
• Add the cooked shallot and meat mixture and combine well.

Shape and bread the croquettes

• Take a scoop of the mixture and press it into an oval.
• Coat it in flour, then beaten egg, then panko.

Fry the croquettes

• Fry the croquettes in hot oil until golden brown.
• Drain on paper towels.

Assemble the sandwich

• Butter the bread slices and spread a generous amount of egg salad between two slices.
• Cut the sandwich diagonally and open it back up.
• Add the greens and a croquette inside.