01 - Preheat the 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 the potatoes with butter, milk, salt, and pepper until smooth. Let cool 5 minutes, then mix in the egg and cheddar.
04 - Spoon or pipe the mashed potatoes into the muffin cups, pressing up the sides and bottom to form a nest. Reserve a little mash to use as a topping.
05 - Bake the potato cups for 15 minutes until they hold shape and the edges start to crisp.
06 - In a skillet over medium heat, cook the sausage, breaking it up with a spoon, until browned. Add onion and garlic; sauté until soft, about 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, then top with a spoonful of reserved mash and a sprinkle of cheddar.
09 - Brush the 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.