What's this salad of gray lumps in white dressing?
This is potato salad, cubes of cooked (boiled) potato in a dressing of mayonnaise. If you are looking to replicate this, the typical cha chaan teng (茶餐廳) style potato salad might have some sweetened condensed milk, something like a 4:1 ratio of mayonnaise to condensed milk. Also, the garnish appears to be half of a cherry tomato, rather than a maraschino cherry.