Preheat oven to 400 degrees F. Line a baking sheet with parchment paper. Place the parsnips on the sheet, and toss with olive oil. Season with sea salt and black pepper, to taste. Bake for 15 to 20 minutes, until slightly brown and tender.
Heat 2 tablespoons olive oil in a soup pot or Dutch oven over medium heat. Add the leeks, and saute for 2 to 3 minutes until fragrant. Add the pears and ½ teaspoon salt, and cook for a few more minutes. Next, add the roasted parsnips, vegetable stock, thyme sprigs, and bay leaf. Bring to a boil, then cover and reduce to a simmer for 15 to 20 minutes.
Remove the pot from heat, uncover, and take out the bay leaf and thyme sprigs. If you have an immersion blender, use that to puree the soup in the pot. If you are using an upright blender, carefully transfer the soup to the blender. Do not fill it all the way (you may need to blend in batches), and leave the lid cracked to let steam escape. You can also remove the lid and cover the blender loosely with a dish towel if needed. Blend until smooth. Be very careful while blending. The mixture will be piping hot!
Serve immediately, garnished with fresh thyme and homemade croutons.
To make the homemade croutons that are pictured in this recipe, preheat the oven to 400 degrees F. Slice preferred amount of sourdough bread or baguette into cubes, and brush the top and bottom of each cube with olive oil. Arrange on a baking sheet, and sprinkle with salt and pepper. Bake for ~10 minutes or until crispy.
Leftovers will last in an airtight container in the fridge for up to 5 days. Reheat in the microwave or in a saucepan over medium-low heat.