Cut potatoes into bite-sized pieces. Put into heatproof container with a little water and cover with plastic wrap. Microwave (if your microwave has settings, select something like "prepping root vegetables"). Combine with butter while hot. Mash and mix well.
Add ● ingredients to the mixture in Step 1 and season. (Adjust the taste to your liking.)
Chop each cube of foil-wrapped cream cheese into fours.
Form potatoes from Step 2 into 11 to 12 small balls. Bury cubes of cheese in their centers and shape.
Combine ingredients for coating in heatproof container used in Step 1. Preheat oven to 210°C. ※Also refer to Step 8.
Coat the potato balls from Step 4 with the coating mixture. (Scoop the mixture with one hand, place the balls on top, and coat as if making onigiri.) Line oven-proof plates with baking paper.
Bake in a preheated oven for 13 to 15 minutes and it's done. ※It won't be undercooked even if the coating isn't golden brown because the filling is already cooked.
[If you prefer the panko golden brown] Dry-fry until browned and mix in some vegetable oil if you want to give your croquettes some extra toasted crispiness.