Peel and finely dice the onion. Knead with the minced meat, paprika, 1 egg, breadcrumbs, mustard, oregano, salt and pepper.
Sprinkle the work surface thinly with breadcrumbs. Roll out the minced meat in a rectangular shape measuring approx. 28 cm x 30 cm. First top with Gouda cheese, then with boiled ham - leave a 2 cm wide border all around. Roll up from the long side, fold in the open ends and press together. Place on a baking tray covered with baking paper.
Bake in the preheated oven (electric oven: 200 ° C, convection: 175 ° C, gas: level 3) for about 1 hour. After 40 minutes, cover with aluminum foil if necessary. Arrange everything in portions on plates and serve hot.