Set the oven to 400 °F and cover two rimmed baking sheets with parchment paper or greased foil. The lining should cover the cooking surface so the meatballs release easily.

Use a large bowl to gently mix the beef, pork, pork rind crumbs, onion, garlic, 1/4 cup heavy cream, egg, salt, and pepper. Stop when the ingredients look evenly distributed and the mixture remains soft.

Portion the mixture into 40 to 50 small meatballs and arrange them on the lined sheets. Keep their sizes consistent and leave space between them for even cooking.

Cook the trays in the oven for 20 minutes, extending the baking time if needed until the meatballs are fully cooked. Check doneness with a food thermometer rather than relying on exterior color alone.

While the meatballs bake, whisk the coconut flour into melted butter in a large skillet. The mixture should look evenly blended, without dry pockets of flour.

Whisk in both broths, the remaining 3/4 cup heavy cream, soy sauce, and mustard, then maintain a gentle simmer for 10 minutes or until the gravy thickens. Look for a smooth sauce that begins to coat the back of a spoon.

If the gravy needs more body, gradually whisk in the optional 1/2 to 1 tsp xanthan gum rather than adding it all at once. Stop adding it when the sauce clings lightly to a spoon but still pours.

Fold the cooked meatballs into the finished gravy and serve promptly, or cover the skillet and hold it over low heat. The sauce should coat the meatballs evenly without bubbling vigorously.