In a stock pot over medium heat, add olive oil. When hot, add leek, potatoes, and carrots, and cook for 8-10 minutes, or until they begin to brown around the edges. Add garlic and cook and additional 30 seconds. Add broth, yellow squash, salt, thyme, celery seed, and pepper. Bring to a boil, cover, and reduce heat to low. Simmer for about 8-10 minutes, or until squash are cooked through and soft.
Remove from heat and allow to cool for 2 to 3 minutes. Use an immersion blender and blend until chunky. Add bacon and cheddar and stir just before serving.
Add desired garnishes, like croutons, pesto, shredded cheese (recommended), or a splash of cream, and serve warm as an appetizer or side dish.
