Pre-heat your oven to 400° F. In a large roasting pan, combine squash, shallot, garlic, bay leaf, thyme, dried chili and season with salt and pepper. Add vinegar and 4 tablespoons of extra virgin olive oil. Lightly toss and roast in the oven until tender and cooked through, about 35 minutes.
Remove from the oven, remove and discard the bay leaf, dried chili and thyme. Transfer to a blender and blend with vegetable stock until smooth. Once smooth, with the motor running, blend in 1 cup of kefir and ¼ cup of extra virgin olive oil. Adjust seasoning to taste and set aside.
In a medium sized mixing bowl, combine remaining kefir with lemon zest, ¼ cup of extra virgin olive oil, salt and pepper and set aside.
- Serve in warm soup bowls with a drizzle of the seasoned kefir sauce.