Place the beef cubes in a large slow cooker. Top with the garlic, carrots, mushrooms and corn.
In a medium bowl, whisk together the beef broth, tomato paste, Worcestershire sauce, and oregano. Pour this into the the slow cooker and stir to combine.
Cover the slow cooker and cook on Low setting for 7 to 9 hours, until the beef is tender.
To make the mashed potatoes, place the potatoes in a large saucepan and cover them with 2 inches of water. Bring the potatoes to a boil over high heat and stir in the salt. Reduce the heat and simmer until the potatoes are tender when stabbed with a fork (start checking them at 15 minutes).
When the beef is tender, use a large spoon to skim any fat from the surface of the beef and veggie mixture in the slow cooker.
In a small bowl, mix the flour and 6 tablespoons (90 ml) water until smooth, then slowly stir the mixture into the slow cooker.
In a small bowl, mix the flour and 6 tablespoons (90 ml) water until smooth, then slowly stir the mixture into the slow cooker. Then add the peas and adjust the seasonings with salt and pepper to taste.
Spread the mashed in an even layer over the top of the beef and vegetables. Cover the slow cooker and cook on high for 15-30 minutes, until the gravy has thickened and the mashed potatoes are heated through.
Serve and enjoy.