Preheat your oven to 400°F (200°C).

In a large mixing bowl, toss diced potatoes with olive oil, salt, and pepper until well coated.

Spread potatoes in a single layer on a baking sheet and roast for about 25-30 minutes, or until golden and tender, stirring halfway through.

In a large pot over medium heat, add a bit more olive oil and sauté sliced leeks for about 10 minutes until soft, but not browned.

Add the roasted potatoes to the pot with the leeks.

Pour in the broth and bring everything to a gentle simmer. Cook for about 15 minutes.

Use an immersion blender to puree the soup until it reaches your desired consistency. Alternatively, carefully transfer the soup to a blender in batches to blend.

Stir in the heavy cream and season with more salt and pepper if needed. Allow to warm through for a few more minutes before serving.