1. Place a 4-quart (or similar) pot over medium heat and add the olive oil. When the oil is hot, add the leeks and cook, stirring often, for about 5 minutes or until the leeks are soft and beginning to brown. Add the garlic and cook for another 1 to 2 minutes. 2. Add the potatoes, salt, and bouillon paste, if using, followed by 5 cups of water. Bring the soup to a boil, then reduce the heat and cover the pot. Let simmer, covered, for 30 to 40 minutes, or until the potatoes are very tender. Meanwhile, make the garlic butter. Place a small saucepan over medium-low heat and add the butter and garlic cloves. When the butter is melted and the garlic is beginning to sizzle, reduce the heat to low and cook, swirling every now and then, for about 20 minutes or until the garlic is golden and the butter is just beginning to brown. 4. To finish the soup, add the greens and let cook covered for 1 to 2 minutes or until wilted. Transfer the soup to a blender or use an immersion blender to puree the soup until smooth. Return the soup to the pot, if applicable, and stir in ¼ cup of heavy cream (off the heat). Serve topped with a small handful of fresh greens, a few drops of heavy cream, and a couple generous spoonfuls of garlic butter. Store leftover soup in an airtight container in the refrigerator for up to 3 days or freeze for up to 3 months. Garlic butter will keep in an airtight container in the refrigerator for up to 1 week.