Peel and cut potatoes into 1- 1 1/2 inch pieces.
Boil potatoes until tender.
In small skillet saute onion and garlic.
Drain potatoes when they are cooked.
Add potatoes to Mixer along with sour cream, butter and milk.
Whip on high until potatoes are smooth.
Add salt and pepper to taste and mix in.
Top with additional butter, sour cream and diced scallions before serving.