In the same skillet, add the butter and the reserved fat. Once the butter is melted, add the shallot and garlic. Sauté until tender, about 2 minutes.
Next, sprinkle the cassava over the shallot mixture and cook, stirring, to toast the flour, about 1 minute.
While whisking, slowly pour in the beef broth 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, coconut aminos, salt, pepper, allspice, 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 a meatball with the sauce and add more salt, if desired. Serve as desired and top with additional parsley.