Whisk together the almond flour, ground flax, sweetener, and baking powder.Using a fork, mix in the beaten egg, butter, and vanilla until a crumbly dough forms. This can also be done in a food processor.Use your hands to work the dough and make sure there are no large pieces of butter left.Roll the dough into balls using about 1 tsp to 1.5 tsp of the mixture per ball and place on your baking sheet. Place in the freezer to chill for at least 15 minutes.Heat oven to 375.Once the cereal balls are chilled, bake for 12-15 minutes on the center rack or lower third to prevent burning.Remove from the oven and toss with optional cinnamon and sugar, or sugar only. Let cool at room temperature for 1 hour (or longer) before eating. The more time the cereal spends drying, the crispier it will become.