Heat oil in saucepan over medium heat. Add garlic, and cook 30 seconds.
Add broth and lentils, and bring to a boil.
Reduce heat, cover, and simmer 10 minutes.
Add potatoes, and cook 15 minutes, or until lentils are tender.
Add spinach, lemon juice, lemon zest, and cayenne pepper.
Cover, and simmer 2 minutes, or until spinach wilts.
Stir in mint.
Season to taste with salt and pepper.
