Wash and cut the courgettes into a 4 mm (0.15 inch) slices.
Prepare the batter by combining all dry ingredients first, then add the plant milk a bit at a time to avoid creating lumps and mix until smooth with a whisk.
Bring to temperature the vegetable oil (see tips and tricks in post) that has to be at least 1 inch above the bottom of the pan.
Coat each courgette slice in the batter, and deep fry for a couple of minutes on each side or until slightly brown and crispy. Arrange on a plate covered with kitchen paper to absorb the excess of oil.
Repeat until you have finished all the slices.
In a jug season the passata with chopped parsley, onion powder, salt and pepper. Mix well.
Start assembling the parmigiana by spreading some tomato paste on the bottom of the tray, cover with a layer of fried courgettes, another layer of passata, followed by grated vegan mozzarella.
Repeat step 7 for 2 or 3 more layers.
Top the final layer with the remaining passata and a generous spread of vegan parmesan cheese.
Bake the vegan courgette parmigiana tray in a 180°C (350°F) preheated oven for 30-40 minutes. Turn on the grill mode in the last 5 minutes if you'd like the top to be slightly charred.
Serve the vegan courgette parmigiana warm or at room temperature. Some say it is even better the day after.