Preheat oven to 400 degrees F. Line a baking sheet with parchment paper. Add pears and parsnips, and drizzle with olive oil. Top with sea salt and black pepper, to taste. Bake for 15 to 20 minutes until slightly brown and tender.
Heat 1 tbsp olive oil in a medium pot over medium heat. Add the diced leek and saute for ~5 minutes. Add the roasted pears and parsnips, vegetable stock, thyme, and bay leaf. Bring to a boil, then cover and reduce to a simmer for 20 minutes
Remove pot from heat. Remove bay leaf and thyme sprigs before transferring mixture to the blender. Blend for ~1 minute, starting at variable 1 and slowly increasing speed until smooth. Be very careful while blending. The mixture will be piping hot!
Serve immediately, garnished with fresh thyme and homemade croutons.