Preheat oven to 375°F.
Add potatoes to a large pot of salted water and Bring to a boil. Cook until tender, about 15–18 minutes. Drain well and transfer to a large bowl.
Add butter, sour cream, milk, salt, and pepper. Mash until smooth and fluffy (don’t overwork).
Fold in cream cheese, jalapeños, shredded cheese, and green onions.
Lightly grease a muffin tin. Spoon mashed potato mixture into each cup, filling to the top.
Sprinkle with cheese and bake for 30 minutes. Broil for 3-5 minutes to finish.
Let cool slightly, then top with fresh chives.

