For the soup, finely puree chickpeas, tomatoes, yogurt, lemon juice and cumin in a food processor or with a hand blender. Refrigerate overnight.
The next day, season to taste with salt and pepper.
For the cucumber-mint salsa, peel and seed the cucumber, cut the mint into fine strips and mix with the olive oil. Season to taste with salt.
Pour the soup into espresso cups and garnish with the salsa. Serve ice cold.