Sweet Pea Soup With Lemon

• 8 sprigs watercress for (garnish)
• 1 onion
• 1 bunch watercress
• 1 pepper lemon pepper cream (freshly ground)
• 1/4 dices
• 950 ml chicken broth
• 240 gr firm-ripe pear
• 240 gr peas (frozen)
• 120 ml sour cream
• 120 gr russet potato