For the aioli, peel and finely chop the garlic. Wash parsley, shake dry and chop. Chop the capers coarsely. Mix everything with salad cream and season with salt and pepper. Peel onion and cut into very fine strips. Grate cheese coarsely.
Preheat oven (electric cooker: 160 °C/circulating air: 140 °C/gas: see manufacturer). Line a baking tray with baking paper, spread the slices of bread with butter. Place 4 slices with the buttered side down. Arrange roast pork, jalapeños, onion, aioli and cheese on top. Cover with the remaining bread slices, butter side up.
Fry the bread in a hot pan without fat in 2 portions on each side for about 2 minutes until golden brown. Cover the breads with baking paper and weigh them down with a pot. Then place on a baking tray and bake in a hot oven for about 5 minutes until the cheese melts.