Make the skillet croutons: In a small bowl, toss chopped bread with olive oil, dried thyme, and a pinch of salt and pepper. Toast croutons in a nonstick skillet over medium heat for 4 to 5 minutes, stirring occasionally. It’s okay if the char on them becomes uneven. Some sides should be crunchy and some soft still. Remove and set aside.

Cook the bacon: Add chopped bacon to a large pot over medium heat. Cook until fat renders out and bacon is crispy. Transfer the bacon to a plate lined with a paper towel and set aside as a topping for the soup. Reserve the bacon grease in the pot.

Make the soup: Add onion, celery, carrots, and parsnip to pot. Season with salt and pepper and cook until vegetables soften, 3 to 4 minutes. Stir in flour, cook for another minute, then add broth and milk. Slowly stir. Bring to a slight simmer, then add potatoes and simmer for about 15 minutes, or until potatoes are very tender.

Blend half of the soup: When potatoes are very tender, remove half of the soup from the pot and let cool briefly. Blend until smooth and return to the pot, stirring it into the non-blended soup base. Alternatively , blend half the soup directly in the pot with an immersion blender; be careful not to over-blend! Some chunks are good. Taste the soup and adjust seasoning to your liking. Keep warm until serving.

Serve: Serve the soup topped with fresh chives, crispy reserved bacon, and skillet croutons. Leftover soup keeps well in the fridge for up to a week, or you can freeze it for 3 months. Reheat gently on the stove with a splash of water.