Fill a large pot with cold water, add salt, and bring to a boil. Add potatoes and cook 15–18 minutes until fork-tender. Drain and let steam dry 2 minutes.
Warm cream with minced garlic on low heat for 3–4 minutes.
Return drained potatoes to pot over low heat, add butter, and mash until smooth.
Add warm cream gradually while mashing to reach a creamy texture.
Remove from heat, drizzle in truffle oil, fold gently, and season with salt, pepper, and Parmesan.
Transfer to serving bowl, drizzle more truffle oil, and garnish with chives and shaved Parmesan.