To prepare the beef
1: Place the fillet of beef on a sheet of cling film and roll tightly in the film to hold the shape. Refrigerate until ready to cook.
Café de Paris butter
2: Put the softened butter into a bowl and add all the herbs, curry powder, gherkin, capers, garlic, shallot and egg yolk. Beat with a spatula until evenly combined, then season lightly with salt and cayenne to taste.
3: Spoon the flavoured butter into a piping bag fitted with a 1cm plain nozzle and pipe onto a sheet of cling film, to form a small log. Wrap in the cling film and roll into a small, smooth cylinder. Tie the ends of the cling film to seal and submerge the parcel in iced water to firm up.
4: When set, slice the butter into 5mm thick discs and remove the cling film. Cover and store in the fridge until needed. (Any leftover butter can be frozen for future use.)
Fried onion rings
5: Slice off the sides of the onion then cut 8 slices from the middle, each 4mm thick. Press out the middles, to leave 8 perfect onion rings. Place the onion rings in a container and pour on the milk to cover. Leave to soak in the fridge overnight to draw out the raw onion flavour.
6: To make the batter, in a bowl, mix the flour and Trisol together then whisk in the sparkling water to make a smooth batter. Cover and leave to stand in the fridge for about an hour before using. When ready to serve, remove the onions from the milk. You will need to fry the onion rings in batches.
7: Heat the oil in a deep-fryer to 180°C. Season the flour with salt and pepper. Dip the onion rings in the seasoned flour and turn to coat all over; shake off any excess. Now dip them into the batter, carefully add to the hot oil and deep-fry for 2–3 minutes until crisp and golden.
8: Remove the onion rings from the pan and drain on kitchen paper. Season with salt and serve.
9: Cut a slice from the top and bottom of each potato, then press an apple corer through from top to bottom to make round cylinder chips. Put the cut chips into a colander under cold running water to wash of some of the starches.
10: Now lay the chips on a steamer tray and season them with salt. Steam for 30 minutes until cooked, then place in the blast chiller to cool quickly and draw out excess moisture, or place in a cool, dry place.
11: Once the chips are cool, heat the oil in a deep-fryer to 140°C. Lower the chips into the hot oil in a wire basket and deep-fry for 10 minutes. Remove the chips from the fryer, drain and leave to cool until needed.
12: When ready to serve, heat the oil to 180°C and deep-fry the chips for about 6–7 minutes until golden and very crispy. Remove the chips from the fryer and drain on kitchen paper. Season with salt and sprinkle with chopped parsley.
To cook the steaks
13: Heat up a large heavy-based frying pan over a medium heat. Cut the fillet of beef through the cling film into 4 steaks (each 250g). Season the top and bottom of each steak heavily with table salt.
14: Add the butter to the hot pan. Once it is melted and foaming, add the fillet steaks, with the outside still wrapped in cling film. Brown the steaks on both sides to a dark fully roasted colour. This will take about 6–8 minutes.
15: Lift the steaks out of the pan, remove the cling film and season the sides with salt. Return the steaks to the pan and colour them evenly all around their sides until they have a dark crust.
16: Once the fillet steaks are cooked medium-rare (or to your taste), lift them out of the pan and set aside on a warm plate in an oven warming drawer to rest for 10 minutes.
17: Return the pan to the hob and add the lemon juice, stirring and scraping to deglaze, then pour the liquor over the resting steaks.
18: Just before you serve the dish, stir the chopped tarragon through the warm hollandaise. Spoon into individual serving dishes. A link to the hollandaise sauce recipe can be found at the top of this page.
19: Once the fillet steaks are well rested, flash them under a hot salamander or grill briefly to warm.
20: Place a steak in the middle of each warmed plate, top each steak with a disc of the café de Paris butter and a couple of crispy onion rings.
21: Serve the chips and béarnaise sauce on the side.