In a large bowl, add the ground beef, cooled mushrooms, egg, and spices, stirring to incorporate.
Add the golden flax seed and stir, and then add the coconut flour, a teaspoon at a time, until the meat mixture holds together and is no longer too wet.
Divide the meat mixture into 10-12 tablespoon sized portions. Place one portion into the palm of your hand and add a cheese slice into the center. Shape the meat around the cheese, making sure to pat the "seams" shut.
Place "seam side" down on a foil or parchment lined baking sheet.
Bake for 10-15 minutes.
Allow to cool 5-10 minutes so the cheese doesn't burn one's mouth! Serve with pizza sauce for dipping, if desired.
Recipe by Following In My Shoes at https://followinginmyshoes.com/bento-2/cheese-stuffed-pizza-meatballs-iheartlunch/