Preheat oven (electric cooker: 225 °C/circulating air: 200 °C/gas: see manufacturer). Clean leek, cut lengthwise, wash and cut into fine rings. Cut ham into thin strips.
Heat the oil. Sauté the leek for 2-3 minutes. Sprinkle with sugar and steam for another 2 minutes. Add ham and fry for 1-2 minutes. Season everything with salt and pepper. Take out and let cool down a little.
Unroll the tarte flambée dough with baking paper and spread with cream cheese. Spread the leek and ham mixture on top. Bake in a hot oven for about 15 minutes. Take out and serve immediately.