Peel and cube the Russet potato, then place in a pot of water and bring to a boil until fork-tender.
While the potato cooks, heat the olive oil in a skillet over medium heat and sauté the diced yellow onion until translucent.
Add the ground beef to the skillet, breaking it into small crumbles with a spatula, and cook until no longer pink.
Stir in the tomato paste, garlic powder, sea salt, and black pepper, then pour in the beef broth to deglaze the pan.
Add the frozen peas and carrots to the beef mixture and simmer for 5 minutes until the sauce thickens into a light gravy.
Drain the cooked potatoes and mash them until smooth, adding a tablespoon of the beef broth if needed for a creamier texture.
Transfer the beef and vegetable mixture into a small oven-safe baking dish or ramekin.
Spread the mashed potatoes evenly over the top of the beef, using a fork to create small ridges for texture.
Place the dish under the oven broiler for 3-5 minutes until the potato peaks are golden brown and crisp.
Garnish with freshly chopped parsley and serve immediately.