Slow cooker broccoli soup

Ingredients

• 1/2 pound broccoli
• 4 cups chicken stock
• 1 onion
• 1 leek
• 2 medium-sized (boiling) potatoes
• 2 large carrots, or smaller ones
• 1 1/2 teaspoon cumin seeds
• 1/4 teaspoon ground cumin
• 1/2 teaspoon whole black peppercorn
• 1/2 teaspoon crushed red pepper flakes
• 1/2 teaspoon cardamom
• 1/4 teaspoon ground ginger
• salt to taste
• Créme fraîche