In a large bowl, whisk ¼ cup of the beef stock with the tapioca starch, garlic powder, onion powder, mace, cloves and 2 teaspoons salt until smooth.

Add the ground beef and gently work the mixture together with your hands until the slurry is evenly incorporated. Roll into 1½-inch meatballs; you should have about 24.

Heat the avocado oil or solid cooking fat in a large skillet over medium-high. Add the meatballs in a single layer (work in batches if needed) and cook, turning occasionally, until browned on all sides, 4 to 5 minutes. Transfer the meatballs to a plate; they will finish cooking in the sauce.

Add the mushrooms and shallot to the same skillet with a pinch of salt. Cook, stirring occasionally, until the mushrooms begin to caramelize and the shallot is soft and translucent, 3 to 5 minutes. Stir in the garlic and cook just until fragrant, about 1 minute more.

Pour in 1½ cups of the remaining stock, scraping up any browned bits from the bottom of the pan. Bring to a simmer, reduce the heat to medium-low and return the meatballs to the skillet.

Simmer gently, uncovered, turning once or twice, until the meatballs are cooked through, 4 to 5 minutes.

While the meatballs simmer: In a small bowl, whisk the remaining ¼ cup of stock with the arrowroot until smooth.

Reduce the heat to low and stir the slurry into the pan, cooking gently until the gravy thickens and turns glossy. This should happen very quickly; avoid a hard boil so the sauce doesn’t get gluey.

Taste and adjust seasoning with more salt if needed. Sprinkle with parsley and serve the meatballs with the mushroom gravy.