Preheat the oven to 400˚F.
Coat the peppers in 2 tablespoons of the olive oil and roast in the oven for 30 minutes. They should soften and be starting to blacken on the outside. If your peppers are still firm, continue to roast until you get there. Once out of the oven, immediately transfer the whole peppers to a large heat proof bowl and cover tightly with plastic wrap. Set aside until cool enough to handle.
In a large dutch oven or stockpot heat the remaining tablespoon of oil over medium heat. Add the onion, garlic and carrots. Sauté until the vegetables start to soften, about 6 minutes. Stir in the thyme, tomato paste and cayenne. Continue to cook for another 5 minutes, stirring frequently.
Once cool, peel the skin off the red peppers and remove the seeds. Add the flesh to the pot along with the chicken stock. Bring to a boil and then turn down the heat and simmer for 20 minutes.
Blend the pot contents in a stand blender or using a hand blender. Leave to cool and keep in the fridge to chill overnight. Serve with a dollop of crème fraiche and a scattering of fresh thyme leaves.
You can easily make this vegetarian by adding vegetable stock in place of the chicken stock.
This soup also works eaten warm. I find it depends on the time of year. In the summertime it is so refreshing eaten cold with a dollop of sour cream or crème fraiche.