Jalapeno mayonnaise can be made up to one week ahead. Keep, covered, in the fridge.
1/4 cup olive oil
2 large red onions, sliced
1 tblsp balsamic vinegar
2 x 400g beef rump steaks
2 cloves garlic, crushed
8 slices pane di casa bread
4 gouda cheese slices, halved
Sliced tomatoes and baby rocket leaves, to serve
2/3 cup whole-egg mayonnaise
2 tblsps finely chopped, drained jalapenos
1 tblsp lime juice
Salt and pepper, to taste
Heat 1 tblsp of the oil in a medium, non-stick frying pan over a medium to high heat. Add onions. Cook, stirring occasionally, for about 15 minutes, or until soft. Add vinegar. Stir for a further 1 minute, or until caramelised. Remove. Cover to keep warm.
2 Meanwhile, to make jalapeno mayonnaise, combine all ingredients in a bowl.
3 Trim steaks. Cut in half crossways. Place between two sheets of baking paper. One at a time, gently pound with a meat mallet until 5mm thick. Cut steaks in half again. Trim off any sinew. Toss with garlic and 1 tblsp of the oil. Season.
4 Brush remaining oil over bread slices.
5 Heat a large, oiled grill plate over a medium to high heat. Cook bread for about 1 to 2 minutes on each side, or until charred. Remove. Keep warm.
6 Add half the steaks to hot grill plate. Cook for about 1 minute on each side, or until tender. Remove. Cook remaining steaks on hot grill plate for 1 minute. Turn over. Top with cheese slices. Cook for a further 1 minute, or until melted.
7 To serve, spread half the bread with mayonnaise. Top with tomato, rocket, steaks, onions and remaining bread.