Preheat oven to 350F for convection or 375F for conventional.
Wash the sweet potatoes and pat dry. Toss with the oil, place on a baking sheet and roast for 45-60 minutes or until soft when pierced with a knife.
Peel potatoes while they are hot using a towel or gloves and pass through a food mill into a bowl. Warm the butter, cream and salt, then add to potatoes and stir until fully incorporated.