Simple to put together, this dish is much like a regular gratin, but by stacking the potatoes upright, it yields more of a satisfying crunch. The dense Black Tapenade marries with both types of potato, as a compliment to the creamy white, and a contrast to the sweet. Add greens like chard or kale to make this a nourishing complete meal.
150ml Early Harvest olive oil
3 red onions, peeled and thinly sliced
2 sprigs each rosemary and thyme, stalks removed, leaves chopped
Salt and pepper
300g sweet potato
500g white potato, such as King Edwards
3 tbsp Black Tapenade
2 pinches chilli flakes (optional)
50g Black Douce olives, stones removed then chopped
Place a medium sized pan on a medium heat, add half the olive oil and when hot, add the red onions, rosemary and thyme. Season with salt and pepper and cook for 15 minutes, or until soft and sweet, turning down the heat if it begins to darken. Remove from the heat and set aside.
Heat an oven to 200C. Slice both types of potatoes as thinly as possible (a mandolin is very useful here, just mind your fingertips) and place in a large bowl. Add the remaining olive oil, Black Tapenade, chilli flakes and a third of the red onions and season well with salt and pepper. Mix with your hands so that every slice of potato is separated and coated in oil.
Take a medium sized shallow baking dish (if the dish is too deep the potatoes wont crisp up as well) or oven proof frying pan and spread the remaining red onions on the base. Stack the potatoes in rows, so they are like dominos that have fallen over, with lots of edges exposed. Cover with foil and bake in the oven for 40 minutes. Remove and carefully removed the foil. Check that the potatoes are cooked by inserting a sharp knife through to the middle and if there is no resistance, they are ready. Turn the oven down to 180C and cook the potatoes for a further 10 – 15 minutes, so that they are crisp and golden on top. Top with the black olives before serving.