Preheat oven to 425. Line a round pie pan with parchment (or spray or rub with olive/coconut oil). Set aside.
First, make the mashed potatoes: Bring a medium saucepan filled 3/4 way with water to a boil. Cube potatoes and add them to boiling water, cooking for 20-25 minutes or until you can easily poke/mash them with a fork. Drain, and add 1/4 cup broth, olive oil or butter and mash the potatoes, adding some extra sea salt and pepper as you do.
Next, cook the beef: in a large skillet over medium-high heat, add a dollop of olive oil. Add beef to cook, stirring around until cooked through. Remove from pan and set aside.
Next, cook the veggies: add carrots, celery, frozen peas and seasonings (including tamari and ketchup) to the "meat pan" next and cook until softened, approximately 10 minutes.
Then assemble your shepherds pie: add cooked veggies and ground beef to the pie pan, mixing around gently to combine them.
Spread mashed potatoes on top of the mixture and smooth with the back of a spoon or rubber spatula. Warm in the oven for 5 minutes before turning to broil for a few minutes until the potatoes turn slightly brown on top. Sprinkle with extra thyme and pepper to serve.