Heat olive oil in a Dutch oven or similar medium/large saucepan over medium heat. Add leeks and potatoes cook, stirring occasionally, until the leeks begin to soften, about 2 to 3 minutes. Add the garlic and cook until fragrant, about 30 seconds. Add the broth, asparagus, salt, and pepper. Bring to a boil, then reduce heat and simmer until the vegetables are tender, 10 to 15 minutes.
With an immersion blender, puree the soup until smooth. (You can also carefully transfer it to a blender or food processor in batches and blend it that way. Be careful as hot soup tends to splatter!) Return the blended soup to the pot and let cool a few minutes. Stir in the Greek yogurt, then season to taste with additional salt and pepper. Remember that if you are adding the bacon on top, it will also be salty, so be careful not to overdo it.
Serve hot, topped with crumbled bacon, a sprinkle of fresh chives, and an extra dollop of Greek yogurt as desired.
To make vegetarian, omit the bacon or try swapping it for the roasted chickpea “croutons” in my recipe for Caesar Shaved Brussels Sprouts Salad. To make vegan: omit the Greek yogurt or swap for a non-dairy yogurt. Omit bacon.
Store leftovers in an airtight container for up to 4 days or freeze for up to 3 m months. Let thaw overnight in the refrigerator, then reheat gently on the stove top or in the microwave.