Step 1

1 Position a rack in the top third of the oven and preheat to 400 degrees

Step 2

2 Place the potatoes on a large, rimmed baking sheet and roast for about 1 hour, or until the skin is browned and a fork easily pierces the flesh

Step 3

3 Transfer the potatoes to a wire rack until cool enough to handle, about 10 minutes; leave the oven on

Step 4

4 Halve each potato lengthwise and place cut side up on a work surface

Step 5

5 If the potatoes are still too hot, use an oven mitt or kitchen towel to hold them

Step 6

6 Using a small spoon, gently scoop out the flesh from each half into a medium bowl, leaving a 1/8-inch to 1/4-inch thickness of flesh in each skin

Step 7

7 Don’t fret if the skins tear a bit, you can still fill them

Step 8

8 Arrange the skins on the baking sheet and return them to the oven for about 10 minutes, or until lightly crisped

Step 9

9 Meanwhile, mash the potato flesh with a fork or potato masher until it’s as smooth as you like it

Step 10

10 Stir in the cheese, sour cream, milk, butter, scallions, if using, salt and pepper until well combined

Step 11

11 Remove the potato skins from the oven and turn the oven setting to broil

Step 12

12 Do not raise the rack

Step 13

13 Using a towel or oven mitt, holding each skin steady on the pan, spoon the mixture into the skins, mounding slightly at the center

Step 14

14 Return the pan to the oven and broil for 10 to 15 minutes, or just until lightly browned on top

Step 15

15 Remove the pan from the oven and sprinkle with the scallions and/or bacon, if using, and serve warm