For the carrot soup, combine carrots and 250ml of the vegetable stock in a small saucepan and simmer for about 5 minutes, until carrots are soft.
Meanwhile melt the butter in a medium saucepan. Add onion and celery and cook and stir for a few minutes. Stir in thyme and peas and pour in the remainder of the stock. Bring to the boil and simmer for 5 minutes.
Take carrots and peas off the heat and let cool down a little. Pour the carrot and stock mixture into a food processor and pulse, until smooth. Press the purée through a sieve back into the saucepan. Clean the food processor and the sieve and repeat with the pea soup.
Heat up the soups again. Add maple syrup to the pea soup and season both soups with salt and pepper to taste.
To serve, ladle pea soup into 4 bowls. Divide the carrot soup between the 4 bowls of soup and add a dollop of creme fraiche. Swirl the soups and the creme fraiche with the back of a spoon, to create a decorative pattern and serve immediately.
For a vegan version of the recipe, just omit the cream fraiche.