Quarter capsicums; discard seeds and membranes. Roast under hot grill (broiler), skin-side up, until skin blisters and blackens. Cover capsicum with plastic or paper for 5 minutes, then peel away skin; chop capsicum coarsely.
Blend capsicum until smooth. Meanwhile, boil, steam or microwave potatoes until tender; drain. Mash potato in large bowl; stir in cream and butter. Add capsicum to mash; stir until combined. Season to taste.