Fill a pot with salted water and bring to a boil. Add potatoes and cook until fork‑tender, about 12–15 minutes. Drain well and return potatoes to the hot pot for 1–2 minutes to steam off excess moisture.
Transfer potatoes to a large mixing bowl. Mash thoroughly with a potato ricer or fork until smooth. Add cornstarch, seasoning and chopped parsley. Stir until a cohesive dough forms.
Scoop about 2 tbsp of potato mixture and roll into a compact ball. Repeat until all of the mixture is used (you’ll have roughly 12–14 balls).
In a deep skillet or pot, heat 2–3 inches of neutral oil to 170 °C (350 °F). Carefully lower potato balls into the oil in batches, taking care not to overcrowd. Fry for 7–10 minutes, turning occasionally, until evenly golden and crispy. Use a slotted spoon to transfer to a paper‑towel–lined plate; season lightly with salt while still hot.
In a small bowl, whisk together mayonnaise and Sriracha until smooth and well combined. Adjust the ratio to taste—more mayo for creaminess, more Sriracha for heat.
Arrange potato balls on a platter. Grate fresh Parmesan over the top, sprinkle with extra parsley, and serve immediately alongside the Sriracha mayo.
