Heat olive oil and butter in a large pot.

Add sliced leeks, cover the pot, and cook on low heat for 10 minutes, allowing them to soften.

Stir the leeks occasionally, then add the finely sliced garlic. Continue cooking for another 30 minutes, or until the leeks are very soft.

Add the rinsed and drained chickpeas to the pot, along with 3 cups of chicken stock.

Bring the mixture to a boil, then reduce heat and simmer for 5 minutes.

Carefully transfer half of the soup to a food processor or blender and process until smooth.

Return the pureed soup to the pot with the remaining chunky soup.

Add the remaining chicken stock to the pot and stir to combine.

Season the soup to taste with salt and pepper.

Garnish with freshly chopped chives.

Serve hot with crusty bread.