Combine all ingredients in a small bowl and whisk well.Season to taste and set aside in the fridge until serving.
For the chips
Using a mandoline or very sharp knife, cut the zucchini into very thin rounds.Toss in a bowl with a good pinch of salt.
Spread the slices out in a single layer on a clean dishcloth for 5 minutes.Take another dishcloth and cover them and press gently to extract as much water out of the zucchini as possible. and garlic together.Mix sumac and salt together.
Heat an air fryer to 180˚C.Coat the air fryer basket or tray with cooking / olive oil spray.
Add enough zucchini slices to sit in a single layer.Sprinkle zucchini with about 1 Tbsp of the grated Parmesan cheese and a little garlic powder. Air-fry until golden-brown, 7 to 8 minutes.
Check the chips halfway through. Small chips may brown and crisp before larger ones.Transfer the chips to a serving plate. Repeat air frying the remaining zucchini.
For the steaks
Preheat a braai on medium high heat.Combine all the ingredients except the mushrooms in a small jug.Blitz with a stick blender.
Place mushrooms steaks on the braai and brush them liberally with the herby garlic oil.Braai until tender and lightly charred all over, basting while you cook.
Serve mushrooms hot off the braai with a pile of zucchini chips, a good dollop of aioli and some more herb oil on the side.Enjoy!