Korokke (Potato Croquettes)

From Misa Nakagawa

2 large baking potatoes
1/2 cup milk
2 Tbsp. butter
1 lb. ground sirloin
2 eggs, hard-boiled and chopped
1 medium onion, diced
2 eggs
1 cup flour
2 cups panko breadcrumbs
vegetable oil, for frying
Tonkatsu sauce for dipping (Bulldog brand preferred)

Peel and chop the potatoes and place them in a large stockpot to boil until fork-tender.  Drain the potatoes and mask with the milk and butter.  While the potatoes are cooling, saute the onion until transparent, and then add the ground sirloin and brown.  Mix the beef in with the mashed potatoes.  Once incorporated, add the chopped egg.  Beat the other 2 eggs and set aside.  Take 2 Tbsp. of the meat and potato mixture and roll in the flour, then egg, and finish with the panko.  Let the croquettes sit for a while before frying in a large skillet with enough oil to mostly cover.  Fry on each side until golden brown and then drain on newspaper or paper towels.  Serve immediately with the Tonkatsu sauce.