In a large bowl, mix together the dry ingredients. Set aside.
In the bowl of a food processor, pulse the garlic cloves a few times and then add the mushrooms. Pulse until the mushrooms are in small pieces. Pour the mushrooms and garlic into a small bowl and add the other liquid ingredients. Mix to combine.
Pour the wet ingredients into the dry and use a spoon to mix them together as much as possible. Once you can no longer use your spoon, use your hands to knead the dough until it comes together into a ball.
Form into a loaf shape approx 30cm long.
Prepare a large enough piece of baking foil or paper, and sprinkle with olive oil. Then place your roast in the middle and wrap tightly.
Place on a pre-heated baking sheet and bake for 60-70 minutes in total.
Rotate the loaf 3-4 times during cooking to ensure that it is evenly cooked. Use a fork to test the roast towards the end of the cooking time.
Once it feels pretty firm, it is done.
Remove from the oven and let stand for about 10 minutes before serving. Enjoy!