Wash potatoes thoroughly and cook in boiling salted water for about 18 minutes. Drain potatoes and let them evaporate in the pot. Place them side by side on a baking tray lined with baking paper and press each one flat with the bottom of a glass, so that the potatoes burst open.
Drizzle potatoes with oil and sprinkle with salt.
Bake in the preheated oven (electric cooker: 225 °C/ convection oven: 200 °C/ gas: see manufacturer) for approx. 20 minutes. Wash chives, shake dry and cut into fine rolls. Remove potatoes from the oven, sprinkle with chives and add vinegar.