Prick the potatoes with a fork and microwave on high for 5 minutes. Rotate and cook another 5 minutes. Test with a knife to make sure they’re done.
Cut the tops off the potatoes and scoop the insides into a bowl, leaving a ¼-inch wall around the skin.
Add the milk, butter and salt to the bowl of potato and mash until smooth. If you’ll be piping the potatoes, place them into a piping bag fitted with a large star tip and reserve for later.
In a sauté pan, heat the oil over medium-high heat. Add the onion and sauté until translucent.
Add the ground beef and cook, breaking into smaller pieces, until browned and cooked through.
Sprinkle the flour over the beef and stir to combine. Add the beef broth, Worcestershire sauce, salt, pepper and frozen veggies to the pan. Bring to a simmer and cook until the sauce has thickened and become glossy. Remove from the heat.
Fill each potato evenly with the beef mixture. Pipe the mashed potatoes over the filling, covering the meat mixture completely. (You might not have to use all of the potatoes.).
Bake for 15 to 20 minutes, or until the tops of the potatoes start to brown.
In step 2, you don’t have to microwave the potatoes if you don’t want to— just bake them instead! Rub olive oil, salt and pepper all over the cleaned potatoes. Place potatoes directly on an oven rack and bake at 425 degree Fahrenheit for 40 to 50 minutes until done.