In a food processor combine broccoli, cauliflower and hashbrowns and pulse a few times until the broccoli is cut into small rice sized pieces. Add in garlic powder, onion powder, egg, egg white, arrowroot powder and salt and pulse a few more times to combine.
Line a baking sheet or plate (whatever fits in your freezer) with some parchment paper. Scoop batter into balls on the parchment paper and lightly flatten into discs with your hands. Freeze for a 4-8 hours or until completely frozen then transfer to a large freezer bag for storing.
When you are ready to eat the patties, place a large skillet over medium heat and add oil to the pan. Cook patties as needed for 4-5 minutes per side until browned on the outside.