Preheat the oven to 220C/200C Fan/Gas 7.
For the wedges, bring a pot of salted water to the boil. Carefully drop the wedges into the pan and boil for 4 minutes, then drain well.
Put the potato wedges on a baking tray with the garlic. Drizzle with olive oil, sprinkle with salt, pepper and the thyme and roast for 30 minutes, or until golden-brown and tender.
For the burger, mix the onion, beef, chilli flakes, salt and pepper together in a bowl. Using your hands, shape the mixture into a patty and rub with olive oil. Heat a frying pan until smoking hot and fry the burger for 4-5 minutes on each side, or until cooked through.
Meanwhile, preheat the grill to high and grill the ciabatta until crisp. Put the burger on the toasted ciabatta and top with any desired toppings. Serve the burger with the potato wedges alongside.