• Preheat the oven to 350°F.
• Heat the coconut oil in a heavy-bottomed skillet.
• Add the onions, sprinkle with the salt, and cook gently for about 5 minutes, until the onions are translucent.
• Remove the onions to a bowl to cool.
• Put the ground beef, mushrooms, Parmesan cheese, and egg in a bowl.
• When the onion mixture is no longer hot to the touch, add it to the meat mixture and work everything together with your hands.
• Shape the meat mixture into 2-inch balls and place the balls on a rimmed baking sheet.
• Bake for 30 minutes or until the meatballs are cooked through.
• To make the gravy, place all the ingredients for the gravy in a saucepan.
• Boil, stirring often, for 10 minutes or until the gravy is thick and bubbly.
• Serve the meatballs with the gravy.

Note

• If using store-bought broth, pour ½ cup of the broth (unheated) into a small bowl.
• Add 1 egg yolk and whisk to combine.
• After the gravy mixture has boiled for 10 minutes, reduce the heat to low and slowly whisk the egg yolk mixture into the hot gravy.
• Continue to heat while whisking until the sauce has thickened; this is somewhat like how hollandaise is thickened but in reverse.