Preheat oven (electric cooker: 200 °C/circulating air: 175 °C/gas: see manufacturer). Drain the cucumber salad. Grease a rectangular casserole dish (approx. 26 x 30 cm).
Cut the rolls in half horizontally and place the lower halves of the rolls in the mould with the cut surface facing upwards, close together. Cover with slices of ham. Spread the gherkins evenly on top. Place cheese slices on top.
Mix remoulade, mustard and fried onions and spread on the cheese. Place the top halves of the bread roll on top. Sprinkle with grated cheese. Bake in a hot oven for about 15 minutes.
Remove from the oven and let it cool for 5-10 minutes. Grease the baking paper and place the greased side of the casserole on top. Place a suitable casserole dish on top or place a board on top, weight down with several tins of preserves or the like for about 5 minutes.
Then remove everything, cut the casserole into pieces and serve.