Mix together the ground flax seed and water. Let it set in the fridge for about 10 minutes. It will form a jelly or egg-like consistency.
Pre-heat the oven to 425 degrees Fahrenheit.
Grease a 9x13 baking dish with 1/2 tbsp of oil. Oil-free method: line the baking dish with parchment paper.
Remove the leaves from the head of cauliflower.
Slice the cauliflower into 1-inch steaks. The edges will probably fall apart, but you should be able to get 4 intact cauliflower steaks from a large head. Cut the stalks off each steak.
Mix together the panko, garlic powder, salt, and pepper in a wide, shallow dish.
Pour the flax seed mixture (or "flax egg") into another wide, shallow dish.
Dip a cauliflower steak into the flax egg, and then press into the panko. Make sure to get the outer edges and both sides.
Place the cauliflower into the prepared baking dish.
Bake, covered, for 15 minutes.
Remove the cover and bake for an additional 20-25 minutes, or until the cauliflower is golden brown and fork tender.
Remove the dish from the oven and add a tablespoon or two of marinara on top of each cauliflower slice. Then add some shredded vegan mozzarella on top of each.
Return to the oven for 6-8 minutes, or until the cheese has melted.
Top with vegan parmesan and garnish with basil.
Serve on top of a bed of spaghetti and marinara sauce.