What's this salad of gray lumps in white dressing? I can identify the green lettuce at the bottom, but not the physical matter under the red maraschino cherry. I happened upon this on Open Rice for a popular Western cuisine restaurant in Central, Hong Kong.

What are the gray lumps?

What white dressing is this?
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.