Ingredients (Serves 2)
For the avocado purée
Start by making the avocado purée. Heat the olive oil in a small frying pan, add the shallot and sweat for 5 minutes, then add the garlic and chilli. Season well and cook for a further few minutes until the garlic is soft. Add the avocado flesh and cook for another 5 minutes, mashing up the flesh with the back of a wooden spoon. Transfer to a bowl and keep warm.
Season the steak on both sides. Wipe out the frying pan and return to the hob over a high heat. When it is smoking hot add the butter, then 1 minute later add the steak and cook for 2-3 minutes each side, depending on the thickness and how you like your steak. Leave to rest for 5 minutes then slice thinly.
Cut open the ciabatta or brioche buns and toast them under a hot grill or in a dry frying pan. Spread the toasted buns with the avocado purée, top with the steak, tomato, jalapeños and salad leaves and serve straight away.