01 - Preheat oven to 400°F. Grease a 12-cup muffin tin with butter or nonstick spray.
02 - Boil potatoes in salted water until fork-tender, about 15 minutes. Drain well.
03 - Mash potatoes with butter, milk, salt, and pepper until smooth. Cool 5 minutes, then mix in egg and cheddar.
04 - Spoon or pipe mashed potatoes into muffin cups, pressing up sides and bottom to form nests. Reserve a small amount for topping.
05 - Bake for 15 minutes until cups hold shape and edges begin to crisp.
06 - Cook sausage in skillet over medium heat, breaking up with spoon until browned. Add onion and garlic; sauté until soft, 3–4 minutes.
07 - Pour in broth, parsley, and thyme. Cook until most liquid evaporates, 3–4 minutes. Cool slightly.
08 - Remove potato cups from oven. Fill each with sausage mixture, top with reserved mash and sprinkle with cheddar.
09 - Brush tops with melted butter. Bake 15–18 minutes more until golden and crisp.
10 - Let rest 5 minutes before removing from tin. Garnish with sliced scallions or chives.