Sweat the onion and leeks

• Place a Dutch oven or large saucepan over medium-low heat and add the butter.
• Add the onion, leeks and a generous sprinkle of salt, cover with the lid and cook gently until really soft, slightly golden and creamy.

Add the aromatics

• Stir in the chopped rosemary and the garlic.
• Cook for a couple of minutes until fragrant.

Add stock and lemon zest

• Pour in the chicken stock.
• Stir in the grated lemon zest.

Poach the chicken

• Add the chicken breasts, making sure they are submerged in the stock.
• Cover with the lid and simmer gently, watching the heat.

Cook the pasta

• Add the pasta shells to the soup.
• Cover again and cook until the pasta is al dente.

Shred the chicken

• Remove the chicken breasts to a bowl and let them cool slightly.
• Shred the chicken with two forks.
• Stir the lemon juice into the soup and take the pot off the heat once the pasta is al dente.

Finish the soup

• Return the shredded chicken to the soup.
• Stir in the parmesan, double cream and a generous crack of black pepper.
• Serve with more parmesan, black pepper and a drizzle of olive oil.