In a bowl combine the mozzarella, cream cheese and butter. Microwave on high for 1 minute to melt (alternatively heat over a double boiler or in a small saucepan directly on the heat to melt).
Stir cheeses and butter together.
In a separate bowl combine the almond flour, Xanthan gum, salt and baking powder.
In a third small bowl combine the egg, flax meal and water. Beat to combine.
Preheat oven to 400 F. Line a baking sheet with parchment paper.
Combine melted cheeses, almond flour and egg and flax mixture in the bowl of a stand mixer. Beat for 1-2 minutes, until everything is incorporated. You can mix everything together by hand as well.
Wet your hands and gather the dough. Divide into 6 parts and roll into balls.
Place on the baking sheet and flatten slightly. Top with sesame seeds (optional).