Place a large pot over medium-high heat, add the butter, and allow it to melt. Add the leek, garlic, and seasoning to taste. Sauté for 3 minutes, until it starts to soften.
Add the diced potato, mix to combine, and sauté for 1 minute. Pour in the stock and bring to a boil. Reduce the heat to medium-low, cover with a lid, and simmer for 30 minutes, or until the potatoes are really soft. Remove the lid and pour in the cream, mixing to combine. Take off the heat.
Use an immersion blender to blend the soup to a smooth purée. If using a regular blender or food processor, let the soup cool for at least 45 minutes first — blending boiling hot soup in a plastic blender or processor bowl risks it expanding from the heat and exploding during processing, which can cause serious injury and damage to yourself and your property. Immersion blenders are the safest and easiest option, and are inexpensive to pick up if you don't already have one. Transfer back over low heat, check the seasoning, and keep warm.
Bacon, Apple & Sage Crust
Place a pan over medium heat, add the butter, and allow it to melt. Add the bacon and apple, and fry for 4 minutes, or until golden, slightly crispy, and caramelised. Add the sage, season to taste, mix well, and fry for 1 minute, or until the sage is crispy. Remove from the heat.
Serve the soup in bowls, top with the bacon, apple, and sage crust, and serve with toasted bread. Dig in.
Chef's Tips
Let the potatoes simmer until they're really soft, not just tender — this is what gives the soup its smooth, velvety texture once blended, rather than staying slightly grainy.Fry the bacon and apple together so the apple picks up some of the rendered bacon fat — it caramelises beautifully and balances the saltiness of the bacon.Fry the sage just until crispy, not longer — it can turn bitter if left in the pan too long, so pull it as soon as it crisps up.
Storage & Reheating
Store the soup in the fridge for up to 5 days or in the freezer for up to 6 months, both in an airtight container. It's best to keep the bacon, apple, and sage crust separate — it'll keep in the fridge for up to 5 days. It can also be mixed through the soup instead, though the bacon will lose its crispness once it picks up moisture. To reheat, place the soup into a pot or pan over medium-high heat and, mixing regularly, slowly bring it back to a boil. Alternatively, reheat in the microwave in bursts, mixing between each one.For a dairy-free or vegan version, substitute the butter for olive oil and the thickened cream for soy or oat milk. The soup won't be quite as rich with these swaps, but will still taste great.