Preheat the oven according to the temp on the packet of your oven fries!

Melt the butter in a large, heavy-bottomed pan over a low-medium heat. Add the sliced onion and a good pinch of salt and cook gently for 25-30 minutes, stirring regularly and reducing the heat if anything begins to catch, until the onion is very soft and gorgeously golden. Add the sugar, balsamic vinegar and thyme, then continue to cook for a further 5-10 minutes, or until the onion is lovely and sticky.

When your onions are about 20 minutes from being ready, bake the fries according to their packet' instructions (you’ll probably need to spread them between two trays!). I like to cook mine in a little oil and salt - but you do you.

Switch your oven to its grill setting. Layer the fries, caramelised onion and gruyere on an ovenproof plate. Pop it under the grill for a few minutes, to melt the cheese.

Finish your fries with a few dollops of soured cream, a sprinkling of chopped chives and a good grind of black pepper. Devour immediately.