For the macadamia feta
, blend the macadamias and water in a high-speed blender for 2-3 minutes. Place the mixture in a nut bag and squeeze out the excess moisture. * Place the nut mixture in a food processor with the lemon juice, olive oil and salt and blend thoroughly until combined. Carefully add more salt or lemon juice, a little at a time to taste, being careful not to add too much.
Line a colander or sieve with cheesecloth and place the mixture in it. Pat the mixture into a small slab that is 2-3cm thick and fold the muslin over to wrap it. Place in the fridge for at least 12 hours to set. Remove from the muslin and cut into 2 x 3 cm oblong pieces. Gently place the pieces in a jar, alternating with the peppercorns, thyme and bay leaves. Pour over the macadamia oil to cover. Cover with a lid and keep refrigerated until ready to use.
For the mushrooms, spinach and tomato sauce, place the tinned tomatoes, butter, 1 clove crushed garlic and salt in a saucepan and simmer over medium to low heat until thick, about 25 minutes. Crush the sauce with the back of a fork to break up any large pieces of tomato and season to taste.
Preheat oven to 180°C and place mushrooms, bottom side down in a single layer in a baking dish. Heat 1 tablespoon of olive oil in a frying pan or wok and add the remaining garlic. Allow to cook for 30 seconds before adding the spinach and cook, tossing, until wilted. Season to taste.
Divide the spinach between the tops of the mushrooms. Add 1-2 tablespoons of tomato sauce over the top, a piece of macadamia feta and sprinkle with finely crushed macadamias. Drizzle the remaining 1 tablespoon of olive oil evenly over the toppings. Place in the oven and cook for 15-20 minutes, until the mushrooms are cooked through and the macadamias and macadamia feta are golden.