Sweet potato: the chameleon of the vegetable world

The sweet potatoes at Ruth's Chris Steak House in Dubai come from Australia, but when first cultivated 5,000 years ago, they grew primarily in the tropical regions of South America.

I know it's long past the holidays, but I haven't been able to put the thought of sweet potatoes out of my head. Blame it on my disappointment the day before Christmas when none were to be found at Spinneys. Blame it on homesickness - a yearning for a southern upbringing I never actually had - but I was certain I couldn't wait until next December to tuck into my favourite holiday side dish. Then I spotted an item on the menu at Ruth's Chris Steak House in Dubai's Monarch Hotel: sweet potato casserole with pecan crust. Here was my ticket to heaven. "It's quite the highlight on our menu," says Paul de Visser, the executive chef for the steak house, which celebrated its first anniversary in January. "The sweet potatoes are a perfect balance for our steaks. The sweet and the savoury go great together."

De Visser, who comes from the Netherlands, admits he hadn't worked with sweet potatoes before joining the steakhouse chain, which operates 140 restaurants worldwide. "There are lots of potatoes in Dutch cooking," explains the young chef, who has the unflappable manner of someone used to serving a packed house. "But not sweet potatoes. They're much more North American." The sweet potatoes at Ruth's Chris Steak House come from Australia, but when first cultivated 5,000 years ago, they grew primarily in the tropical regions of South America. Now they're grown wherever temperatures are warm enough - the plant can't tolerate frost - and where there's enough water to support their growth, places such as China, New Zealand and North Carolina. Only distantly related to the potato, the sweet potato is often confused with the hairier, darker yam, which is native to Africa and Asia.

Both are delicious, of course, but the large, starchy root vegetable known as sweet potato has perhaps even more going for it. Besides being rich in complex carbs, fibre and vitamins A (beta carotene) and C, the sweet potato is like a chameleon, adapting to pots of all persuasions. In Uganda, sweet potatoes are sliced, sun-dried and eaten for breakfast with peanut sauce and a cup of tea. In China, they're baked in a large iron drum and sold during the winter as street food. In Japan, chunks are dipped in tempura batter and fried.

Then, of course, there's the all-American side dish: sweet potatoes mashed and sweetened with brown sugar, maple syrup or molasses and dotted with mini-marshmallows. Ruth's Chris Steak House, with roots back to late-1920s New Orleans, serves a down-home southern version, thankfully minus the marshmallows. It's a great sidekick to a prime-American steak, though some guests, de Visser admits with a smile and a shrug, "order it for dessert with a scoop of vanilla ice cream".

The recipe, from Ruth's Chris Steak House, calls for steaming the unpeeled sweet potatoes whole; but to save time, you can peel and slice them into 1-cm discs first. Serves 6. Ingredients 1kg sweet potatoes 330g caster sugar (but I chose to use as little as 165g) 1 tsp salt 2 tsp vanilla 4 eggs 200g salted butter, melted 65g pecans, finally chopped 2 tbsp brown sugar 55g plain flour 30g salted butter, softened

Method Butter a 25cm square glass pan and set aside. Steam the unpeeled sweet potatoes for at least 30 minutes or until completely cooked, testing with a fork for tenderness. Remove them from the steamer and place in a bowl in the fridge to cool for easier peeling. Preheat the oven to 170°C. When cool enough to handle, peel the skins from the potatoes and place them in a mixer bowl. Beat them on low-speed until well blended. Add the sugar, salt and vanilla and beat at medium speed for two minutes. Crack the eggs into a small container, then add, one by one, to the sweet potato mixture, scraping down the bowl with a spatula. Add the melted butter, mixing to combine thoroughly. Spread the mixture in the pan and place it on a baking tray before putting it in the oven. Set the timer for 20 minutes. While the casserole is baking, prepare the pecan crumble: combine the pecans, sugar and flour with a fork in a small bowl, then cut in the softened butter until the mixture is crumbly. Place the crumble on a foil-lined toaster oven tray and bake at 170°C for five minutes. When the timer goes off on the casserole - by now it should just be turning golden in some places - sprinkle the crumble evenly on top and bake for another five minutes.