Preheat oven to 375°F and grease muffin tin with butter or spray.
If needed, make mashed potatoes and let them cool to warm.
Combine mashed potatoes, sour cream, cheese, eggs, melted butter, and seasonings in a large bowl.
Fold in half of the bacon and most of the chives.
Scoop mixture into muffin tin, about ¾ full, and create a small indent on top.
Sprinkle with remaining cheese and bacon; press gently.
Bake for 25–30 minutes until golden and edges pull away.
Let cool 5 minutes, then remove gently and garnish with chives.