- Preheat the oven to 200°C (400°F).
- Melt butter in a large saucepan over medium-high heat. Add mushrooms and fry, without stirring too often. Cook until nicely coloured, about 7 to 8 minutes.
- Add the potatoes and broth and cook until potatoes are tender and have absorbed all the broth, about 15 minutes. If potatoes are still too hard, add more broth.
- Add the cream and stir gently. The potatoes will absorb the cream.
- Add the Parmesan and thyme, and then place under the broiler for 5 minutes to melt the cheese.
For thin slices of potato, cut it using a mandolin.
By not stirring the mushrooms too much, we produce less liquid resulting in nicely coloured mushrooms.