1) Heat the olive oil in a large saucepan over medium-low heat. Add the yellow peppers, leeks, garlic, salt and turmeric, and cook, stirring occasionally, until the vegetables begin to soften, about ten minutes.
2) Tie the parsley, thyme and bay leaf together with kitchen string. Add the potato, water and herb bundle and bring to a boil, then reduce the heat and simmer, uncovered, until the potato is very tender, about 20 minutes.
3) Discard the herb bundle. Puree the soup in small batches in a blender (keep the lid cracked to allow steam to escape) or in the saucepan with an immersion blender, until smooth. Return to the saucepan and reheat. Stir in the vermouth and season, to taste, with salt and pepper.