Add the potatoes to a large pot of salted boiling water. Boil until fork tender. Remove from heat and drain.
Mash the potatoes with sour cream, and butter. Add the milk sparingly, the mashed potatoes should be relatively stiff. Stir in the green onions. Salt and pepper to taste.Allow the potatoes to cool completely.
Put the corn flakes in a zip lock bag and crush to a coarse consistency. Transfer to a large soup bowl.
Take the mashed potatoes and divide into ¼ cup increments. Roll into balls. Roll each ball in the corn flakes. If the corn flakes don't seem to stick, brush the potato balls with a bit of sour cream or greek yogurt.
Place the croquettes separated on a sheet pan lined with parchment paper.Bake in a preheated oven at 350℉ for 35-45 minutes, until coating is crisp.