Separate the carrots so that the smaller ones are grouped together on one sheet pan and the larger ones are together on the other pan. The pans will be put in the oven at different times so that the smaller carrots do not burn. Coat the carrots with one tablespoon of olive oil per pan and season with salt and pepper.
Put the larger carrots in the oven for 10-12 minutes. Turn the carrots over so that they are uniformly roasted.
Add the shallots to the sheet pan with the smaller carrots and toss together to coat all vegetables with the remaining tablespoon of olive oil. Place in oven with the other sheet pan and continue roasting for another 20-30 minutes. The cooking time is dependent on the size of the carrots.
While the vegetables roast, warm the chicken or vegetable stock in a large pan. Add the bay leaves and thyme sprigs to the stock.
When the carrots and shallots are browned and nicely roasted, take out of the oven. Add the vegetables to a blender. Add some chicken or vegetable stock so that the carrots and shallots puree easily. Be careful of blending a hot liquid. Make sure the lid is on securely. It isn't a bad idea to hold the lid down with your hand. Once smooth, pour the puree into the pan with the remaining stock.
Heat over a low/medium flame. The soup will bubble and spurt. Occasionally stir until the soup is hot.
Add the cider vinegar and cream. Stir to combine completely. Adjust the seasoning to your liking and make sure to remove the thyme stalks and bay leaves before serving.
If you are making a vegetarian version of the recipe, eliminate the cream. Add more vegetable stock instead.