Clean the mushrooms with a damp kitchen towel and chop any large pieces.
Dissolve stock cubes in boiling water. Rinse the hominy thoroughly in a colander and set aside.
Heat oil in a large saucepan over medium heat. Add some mushrooms and sauté for about 5 minutes.
Add the stock and remaining water (up to 1.5 litres total). Stir in onion, garlic, and oregano. Simmer for 15 minutes.
Add the rest of the mushrooms and the hominy. Season with salt.
Cook for 30 minutes, until the hominy is tender but still has a slight bite.
Serve hot in bowls and top with chopped onion, shredded lettuce, chilli flakes, and a generous squeeze of lime juice.