Make these sticky onions ahead and store chilled for up to five days. They make a perfect partner for hotdogs, burgers and grilled meat dishes
Heat the unsalted butter and olive oil in a frying pan over a medium-high heat and fry the onions with the light brown soft sugar for 10-12 mins until starting to caramelise. Pour in enough boiling water to cover. Turn up the heat and bubble until the water has evaporated, about 10-15 mins. Reduce the heat. Stir in the crushed garlic cloves. Cook for 1-2 mins, then add the harissa. Cook for 1-2 mins and season with a pinch each of salt, pepper and the lemon zest. Will keep chilled in an airtight container for up to five days.
