Preheat the oven to 400F and line a baking sheet with foil or a Silpat.
Heat a large skillet over medium heat and add 1 tablespoon of the butter. Then, add the onion and garlic and saute until golden brown, about 7 minutes.
Remove the pan from the heat, and add half of the onion and garlic mixture to a large bowl.
To the bowl, add the ground turkey, mustard, coconut sugar, 1 teaspoon of the salt, 1/2 teaspoon of the pepper, nutmeg, egg, and almond meal. Mix the meatball mixture together well.
Using a medium-large sized cookie scoop, scoop balls of the meatball mixture onto the baking sheet. Each meatball should have about 2 tablespoons of the mixture in it. Roll the meatballs between your hands to make them evenly shaped.
Arrange the meatballs on the baking sheet so that they don’t touch each other. Bake the meatballs for 18 minutes, remove them from the oven, and set aside.
Make the gravy:
While the meatballs bake, add the remaining butter to the skillet with the onions and garlic and let it melt over medium heat.
Sir in the arrowroot powder, remaining salt, and remaining pepper. Cook this for about 2 minutes.
Add the beef broth and whisk the gravy constantly until no clumps of flour remain. Shake in the Worchestershire sauce and keep whisking the gravy, scraping the edges of the pan frequently.
Once the gravy starts to bubble and thicken to the desired consistency, add the sour cream and stir it in completely before adding the meatballs to the pan.
Remove the saucepan from the heat and add the meatballs. Spoon the gravy over the meatballs so they’re all covered. Serve alone, over egg noodles or spaghetti squash.