St. Patrick's Day: Champ (Mashed Potatoes with Spring Onions)

Ingredients

6 pounds Yukon gold potatoes (large size)
1 pound sweet unsalted butter
3 cups half and half
1 bunch spring onions or scallions
salt to taste

Method
Peel the potatoes, and cut into two by two inch pieces. Place them into a large pot with enough cold water to cover them and not be crowded. Add salt to the water. It should taste like the sea. Bring the potatoes up to a boil and check. They are done when they are easily pierced with a knife. Drain into a colander. Let the potatoes drain and steam for a few minutes. While they are draining cut the butter into small cubes, and heat the half and half on the stove. Pass the potatoes and the butter through a food mill. Add the half and half and mix into the potatoes using a spoon or whisk. Taste the puree and adjust the seasoning to your desired taste. Pass the puree through a fine mesh strainer, chinois or tami is preferable. Slice the spring onions into thin rings and mix into the potatoes when ready to serve. If not serving immediately refrigerate the potatoes and warm with a little additional half and half or milk. The puree can be made the day before.