Nine years ago, interiors specialist Catherine Pawson saw a real estate listing for a 17th-century estate in rural Oxfordshire. With its sprawling fields, a farmhouse, horse stables, and a pond, the home offered solace from the city of London, where Pawson lives in Notting Hill with her husband, John, the celebrated British architect. Despite the property’s ramshackle state, they bought it, and spent the next five years transforming the premises into a pastoral retreat where they could entertain family and friends—often, over refined, low-key meals made by Catherine.