How to Make It
Heat the olive oil in a large nonreactive skillet. Add the diced red bell pepper and minced garlic and cook over moderate heat, stirring constantly, for 2 minutes. Add the sliced mushroom and chicken stock and cook, stirring occasionally, until tender, about 5 minutes. Stir in the lemon juice, season with salt and pepper and let cool slightly.
Arrange the watercress on a large plate and spoon the mushrooms on top. Sprinkle with the mint and serve.