Place the chicken on a baking tray, rub with a little of the butter, season and cook under the grill for 15 mins, turning once until cooked through.
Mix together the remaining garlic butter and breadcrumbs. Remove the chicken from the grill and top each breast with a smear of the breadcrumbed butter. Return to the grill and cook 3-5 mins until the breadcrumbs are golden and the butter melted. Serve any buttery juices, alongside new potatoes and peas or broad beans.