Peel potatoes wash and half them, fill a pot with water and keep potatoes in it, add salt make sure potatoes are covered with water...
Boil till potatoes are done, should be soft enough can mash with hand...
Pass through strainer, let all water strained out...

Keep them in a bowl, mash with potato mash, add half of hot milk, butter, black pepper and tarragon beat with whisk till creamy, remove on casserole, make peaks like with your fingers...
Put few small dollops of butter and sprinkle tarragon...

Serve hot or if you made earlier, while serving put in oven for 5-10 mins, to serve hot mashie