Boil potatoes in a large stock pot on high heat until fork soft. While they are cooking prepare beef.
In a large saucepan add beef and cook for about 5 minutes on medium-high heat. Strain all the fat, then add the 1 tsp. salt, onion and garlic and cook until beef has no pink pieces.
Add carrots, beef broth, Worcestershire sauce, thyme and ¼ teaspoon ground pepper and bring to a boil. Allow it to simmer on low until most of the liquid is gone.
While the beef is simmering, mash your potatoes with ½ stick salted butter, and ½ teaspoon of salt and pepper (or more if desired).
Pour in milk and mix well and set aside.
Once the beef mixture has almost no broth left pour in a can of peas and stir to combine.
Add the beef mixture to the slow cooker, then evenly spread the potatoes on top.
Cook on low for 4 hours and allow to cool slightly, then serve.