To prepare the steaks: Brush a little oil over the steaks, season and set aside while you cook the onions.
To cook the onion: Heat a tablespoon of oil in a large frying pan over a medium heat. Sauté the onion until softened, this will take about 10 minutes. Add in a tablespoon of the sherry vinegar and a little salt and continue to cook for another five minutes until the vinegar has evaporated. Set aside.
To cook the steaks: Heat a griddle pan until hot. Place the steaks, two at a time on the pan and cook for two minutes on each side for rare or until cooked to your liking. Leave to rest for a couple of minutes before serving.
To make the herb oil: Combine all the dressing ingredients in a small bowl. Mix well, taste and season.
To prepare the crème fraîche: Stir the chopped herbs into the crème fraîche, season and taste.
Brush the bread with a little oil on each side and toast under the grill.
Serving Suggestions
To serve: Spread a little crème fraiche over each slice of bread, then spoon over the onion mixture, add some rocket leaves, then slice the steak and lay on top. Arrange some more rocket leaves on top, add some shavings of cheese and a drizzle of the herb oil. Serve immediately.