Drain the pineapple well in a sieve. Clean and wash spring onions and cut into fine rings. Mix flour, eggs and milk until smooth. Season with salt and pepper. Let the dough swell for about 10 minutes.
In the meantime heat oil in a pan, sauté spring onions briefly while turning, season with salt and pepper and remove. Cut mozzarella into slices. Quarter the ham slices. Line a fat pan (32 x 37 cm) with baking paper.
Stir mineral water into the pancake batter and pour evenly onto the fat pan. Bake in the preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: level 2) for approx. 8 minutes. Take out, spread spring onions on top.
Cover with pineapple, ham and mozzarella, spread with sauce and bake at the same temperature for another 10-12 minutes. Remove from the oven, cut into pieces and serve.