Silky sweet potato mash

Name: Silky sweet potato mash
Prep time: 10 min
Cook time: 25 min
Total time: 35 min
Cuisine: American
Ingredients: 500 g water; 600 g sweet potato, peeled and cut into pieces (approx. 3 cm); 30 g salted butter, plus extra to serve (optional); 30 g pouring (whipping) cream; 1 tsp salt; ⅛ tsp ground black pepper; fresh flat-leaf parsley, leaves only, chopped, for garnishing