Add cauliflower florets to a food processor and blend until it reaches a rice consistency.
Transfer cauliflower rice to a microwave safe bowl and microwave 5 minutes at a time 4 times, stirring in between. This will help to draw out the moisture. Allow the microwaved rice to cool for about 30 minutes, until cool to the touch.
Combine cauliflower rice with egg, parmesan and garlic powder.
Divide mixture into 4 portions.
Flatten out each portion into a ¼–1/2” square “bread” shape on a baking sheet lined with parchment.
Bake at 450 Fahrenheit for 15–20 minutes, until golden brown. Allow to cool for 15 minutes before removing pieces from the pan.
Use a spatula to remove the cauliflower bread and assemble sandwiches. Place 1-2 slices of cheese in between two slices of cauliflower bread.
Place in a toaster oven for 5-10 minutes on broil until the cheese is melted and bread is toasty.