Preheat the oven to 350 degrees F and prepare a flat baking sheet by lining it with foil.
Squeeze as much water out of the steamed cauliflower as possible. Press it inside a fine mesh sieve or squeeze it in a piece of cheesecloth until it is nice and dry.
Place the cauliflower rice in a bowl along with the egg, ½ cup of grated cheddar cheese, dried basil, oregano and ground black pepper. Stir the mix well.
Spread the cauliflower mix on the tray, keeping it as square and flat as possible. The mix should be about ½ and inch thick.
Bake in the preheated oven for 10 minutes. Remove the pan from the oven and cut the cauliflower sheet into eight squares to be the “bread” for your grilled cheese.
Place the butter in a large skillet and then lay a slice of the cauliflower “bread” in the pan. Top the bread with about ½ cup of the grated mozzarella and 1/3 cup of the grated cheddar cheese. Place another piece of the cauliflower bread on top to make your grilled cheese sandwich.
Cover the saute pan and cook for about 2 minutes. Remove the cover, flip the bread, and cook for another 2 minutes to fully melt the cheese.
Once the cheese has melted, remove the sandwich from the pan and serve while hot. Repeat the cooking process with the remaining bread and cheese to make 4 grilled cheese sandwiches.