I make this before work all the time. It takes about 5 minutes to prep and 15 minutes to cook.
In a small bowl I mix 2-3 garlic cloves (we LOVE garlic) sliced fresh mushrooms and fresh spinach leaves and a titch of olive oil. Sea salt and fresh ground pepper.
I line a pan with tin foil, add the fish and the above mixture in a bowl and seal the tin foil.