Remove the stalks from the mushrooms and discard. Place the mushroom caps into the freezer for 10-15mins (this will make them easier to slice thinly).
Once the mushrooms are chilled, slice them very thinly (a mandoline is ideal for this, but a sharp knife and a steady hand will do) and arrange the slices onto plates.
Sprinkle with the mint.
For the dressing, place all of the dressing ingredients into a food processor and blend to combine.
To serve, drizzle the mushroom slices with the dressing, then add a spoonful of crème fraîche to each plate.
Sprinkle with freshly grated or shaved pecorino cheese and season well with salt and freshly ground black pepper.
