Carefully chop the sweet potato into 1cm (½in) cubes. Next pour the extra-virgin olive oil into a large, flameproof casserole dish and heat. Add the onion and sauté for 2-3 minutes. Then stir in the sweet potato, red pepper, jalapenos, cumin, coriander and chilli and sauté for a further 3-4 minutes.
Add the remaining stew ingredients and simmer uncovered for 20-30 minutes. Cover, then simmer for a further 35-40 minutes.
While the stew is cooking, combine the crème fraîche, coriander, lime juice and zest and refrigerate until ready to serve.
Using a ladle divide the stew between individual bowls and then top with a dollop of the crème fraîche mixture. Serve with the corn chips.
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