We are champions in making potato "croquettes" as we call them in my country. You need to add a little egg yolk in the hot potato mix.
Croquettes made from approx. 800 grams of boiled potato;
Use preferably floury potatoes. Peel and cut the potatoes in chunks of somewhat the same size. Boil your potatoes in slightly salted water for a little longer than usual, let's say 25-30 minutes. Let the drained potatoes dry a while on low fire while shaking the cooking pot. Mash finely while hot, preferably through a foodmill. Still while hot, add no more than half a tbsp. worth of butter and one egg yolk (the yolk is a must to keep it all together!). Use a rubber spatula or a wooden spoon and quickly fold it all nicely together, taste and adjust with salt, pepper and nutmeg. Cover and refrigerate, if possible overnight. You could add a little purée of garlic and fold that in as well. Don't know about the kale, don't know what kale adds to the croquettes.
Roll balls. Get yourself 3 plates; one with flour, one with beaten egg, one with breadcrumbs. Roll the balls through the flour, egg and breadcrumbs. Let dry for a while.
Deepfry at 180°C (around 350°F), not too many at a time, until golden brown.