Peel the potatoes and cut them in four pieces. Big pieces will suck less water, sure they take a bit longer to cook, but we are here for the taste, not time, right? :) Put the potatoes in a pot and cover them with cold water. Add some salt and bring to a boil. Reduce heat and let them simmer for a good 15 minutes. They are done when they are soft (pierce them with a knife for test).
Drain the potatoes. You can return them on heat for a while so all the water goes away, just don't burn them. Add half milk half cream mix, butter, salt, and pepper. Now its time to mash the potatoes. Stir in cheddar cheese and cook your mashed potatoes for a few minutes so the cheese melts.
At the end mix in sliced green onions. Or as I said before - you can thinly slice the onions and then fry them for a while on oil of butter. Then just mix them in at the end. But ways are good, but the end result is a bit different with each of these cheddar and onion mashed potatoes recipes.
Recipe by Mashed Potatoes Recipe at http://www.mashed-potatoes-recipe.com/cheddar-and-onion-mashed-potatoes-recipe/