In a large bowl, combine the beef, pork, Dijon mustard, parsley, onion, garlic powder, allspice, nutmeg, cayenne pepper, salt, pepper, cassava flour, and egg. Mix until just combined.

Use a tablespoon or small cookie scoop to form and shape 1-inch balls.

Heat the oil in a large, deep non-stick skillet set over medium heat. Working in batches to avoid overcrowding, sear the meatballs in a single layer and cook until browned on all sides, about 2 minutes per side. Transfer the cooked meatballs to a paper towel-lined plate, and continue cooking the rest of the meatball, adding more oil to the pan if it becomes dry. Set aside.

Discard all but 2 tablespoons of excess fat. Melt the butter in the same skillet. Add the shallot and garlic and sauté until tender, about 2 minutes.

Add the cassava flour and cook, stirring, to toast the flour, about 1 minute.

Slowly pour in the beef broth, whisking constantly, until well incorporated and smooth. Add the coconut milk and continue to whisk until well incorporated. Bring the gravy to a simmer, then reduce to a light simmer, about medium-low heat, until you see the sauce start to thicken, about 2 minutes.

Add the Dijon mustard, coconut aminos, salt, pepper, allspice, and apple cider vinegar and stir to combine. Nestle the meatballs back into the skillet. Continue to cook, uncovered and simmering, until meatballs are cooked through, 6 to 7 minutes.

Taste and season with more salt, if needed. Garnish with additional parsley and serve.