In a small bowl add the yogurt, sesame and cumin and mix well to make a smooth paste. Add the cucumber, carrot and salt. Set aside.
Heat the oil in as small skillet over medium heat. Add the mustard, nigella, and chile and cook for about a minute, stirring until the spices are aromatic. Add the cayenne and turmeric. Stir and pour the flavored oil over the cucumbers; toss gently.
Add the lemon juice and chill.
Serve cold topped with mint leaves.