Finely slice the mushrooms. Peel and grate the garlic and ginger. Warm a pan for 1 min. Add 1/2 tbsp olive oil and the mushrooms. Season with a little salt and pepper. Cook and stir for 8-10 mins over a medium heat till the mushrooms and juicy and a little browned.
Stir the garlic and ginger into the mushrooms. Squeeze in the Thai red curry paste. Stir everything together. Add the coconut milk and 200ml boiling water. Cover and bring to the boil. Turn the heat down and gently bubble for 2-3 mins to finish cooking the mushrooms.
Taste the soup and add more salt and pepper if you think it needs it. Ladle into warm bowls to serve.