Boil 6 cups water with 1 teaspoon salt in a large pot. Add 8 ounces (half a package) of kale, stirring to submerge. Boil gently, partly covered, for 10-12 minutes, stirring once or twice to ensure even cooking. Drain in a colander and set aside. (Save the rest of the kale for another use.)
In same pot (no need to wash it), prepare instant mashed potatoes according to package directions for 6 servings, using 1-2 tablespoons more butter than is called for, and adding onion powder, garlic powder, nutmeg and a few grindings of black pepper to the water at the beginning of the recipe. Stir chopped green onions in at the time you stir in the potato flakes.
Immediately stir cooked kale into the hot prepared potatoes, adding additional milk if it needs to be a bit looser for easy stirring.
Taste and add additional salt and freshly ground pepper to season to your taste.
Note: Colcannon is an Irish dish of mashed potatoes and a leafy green (often kale or cabbage), seasoned with butter. In England, the dish is called Bubble and Squeak.