Cheesy Leek & Potato Soup with Cheesy Croutons

1. Heat the butter and oil in a deep, heavy-bottomed saucepan over a medium-high heat. When the butter is melted and sizzling, tip in the leeks and a generous pinch each of salt and pepper. Cook, stirring often, until the leeks are completely softened (about 8 minutes) before stirring in the potatoes, garlic and herbs. Cook for a couple of minutes, until the garlic is fragrant, then pour in the stock. Bring to a simmer and reduce the heat to medium – low. Cook, uncovered for 25 minutes, just until the potatoes are easily crushed with the back of a wooden spoon.
2.  Meanwhile, turn the oven on to 200°C. Arrange the bread in a single layer on a small baking sheet. Drizzle with oil, then toss with the 50g of cheddar and black pepper. Slide into the oven to roast for 10 minutes, turning twice, until the croutons are golden and crisp. Set aside.
3. Remove the soup pot from the heat, and lift out the herbs. Tip in the 100g of grated cheddar. Blitz with a stick blender until smooth, then squeeze in the lemon juice to lift the flavour and adjust the salt and pepper until it tastes just right.
4.  Ladle the soup into warm bowls and top with the crunchy croutons.

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(Any extra soup can be kept in an airtight container in the fridge for up to 5days, or freezer for 3 months).