Preheat oven to 160C/320F.
In a small ramekin, place your garlic bulb inside with a generous drizzle of olive oil, salt and pepper. Bake low and slow for 1.5-2 hours or until the garlic is golden brown and soft.
Place the bacon strips onto a baking tray and also into the oven until the bacon is golden brown. Mince the strips or leave it whole if you prefer.
In a pot over medium heat, melt 2 tbsp of butter. Add in the leeks and onion, sweat until soft and translucent.
Squeeze out the roasted garlic into the pot, followed by the potatoes, rosemary, stock and water. Simmer until the potatoes are soft and cooked through, then fish out the rosemary sprig.
With a stick blender (or a standing blender), blend your soup until smooth. Serve the soup into bowls with the crispy bacon bits, a drizzle of olive oil and parsley.