Greaseproof paper and a rolling pin means that you don't have to have the world's best knife skills!
Wafer-thin fillet steak is tender to the point of almost melt-in-the mouth consistency, when prepared this way and perfectly complimented by the rich mustardy dressing, peppery rocket, slivers of salty parmesan and tiny capers that give little bursts of flavour in your mouth.
Simple to make, no cooking necessary (although you can optionally quickly sear the very outside of the beef, see method) and an elegant dish which could be a light lunch, or a delicious starter.
This serves two people (but is easily doubled), at 265 calories per serving (if you're counting - calories in square brackets).
170g (6oz) fillet steak - ideally you want a piece from the middle, which is one whole cylindrical piece that will slice easily against the grain, trimmed of any excess fat or sinew on the outside (if you're buying it from a butcher, tell them what you want it for) 
Oil to sear beef in, if searing (optional - 1 tsp is 45 calories, e.g. sunflower oil, olive oil) 
50g rocket (arugula) - preferably the small, wild leaves 
14g parmesan shavings - shave them wafer thin yourself, with light strokes of a vegetable peeler down the
side. This doesn't sound like much, but trust me, it's plenty, flavour wise! Keep chilled until serving. 
1 tbsp small capers (Nonpareille), rinsed 
Salt (preferably flaky sea salt e.g. Maldon if you have it) and freshly ground black pepper 
For the dressing
1 tbsp extra virgin olive oil 
1 tsp lemon juice 
1 tsp white wine vinegar 
1 ½ tsp smooth Dijon mustard (e.g. Maille or Grey Poupon brand etc. - not the brown coloured 'French Mustard') to taste - I use 2 tsp (check for gluten, if cooking gluten free - Maille is GF) 
Salt and pepper
You will also need greaseproof paper.
Carpaccio is essentially raw, sliced meat. There is no need to sear the beef, but it's something I like to do, just to elevate the flavour slightly, by getting that hint of caramelised crust on the very outside of the beef.
Whether or not you're searing your beef, wash it and pat dry before you do anything else, as any bacteria will be on the outside of the beef (unlike chicken and pork etc., where they're all throughout, if they're there). This is another reason I like to quickly sear my beef.
To sear the beef without cooking it, you need to get a heavy based pan really, really hot (check by flicking some water in and seeing if it sizzles instantly), add the oil, then using tongues, or a couple of forks add the beef and sit for a few seconds on each side until you have *just* browned it, then remove immediately.
To slice the beef, it's easiest to firm it up in the freezer first (although you can slice and serve immediately from serving, or from the fridge if you like). If you wrap it tightly in cling film before you put it in the freezer, it will have a closer texture and more uniform shape that will also make it easier to slice. Give it about an hour to firm up, depending on the size of your steak. Don't worry if any of it has started to freeze slightly, as it will be defrosted by the time you have sliced it and 'battered' it out.
While you're waiting for your beef to firm up in the freezer you can make the parmesan shavings if you like (keep chilled until serving - or just shave straight onto your carpaccio when plating up) and the dressing.
For the dressing, whisk together all the ingredients with a little salt and pepper, in a bowl big enough to toss the rocket in too, and set aside.
Put another sheet of greaseproof paper on top, then using a rolling pin, gently bash them out until they're flattened to your liking - don't be too enthusiastic with the rolling pin, or you'll be pulling shreds of beef off the paper! You can use a light rolling motion with gentle pressure as well as bashing them once they're getting flatter.
Carefully peel back the top layer of paper (if any stick to it, just use a flat-bladed knife to separate them), You can actually plate up the beef several hours in advance if you want to, cover, and then refrigerate until required, then continue with the following steps. You could also serve it up all on one large plate, as part of a buffet, or sharing platter for people to help themselves to.
then arrange the slices of beef on two serving plates - use a flat-bladed knife, or metal spatula to help lift them off (you can leave a gap in the middle for the rocket).
Scatter the capers over the beef, together with a few flakes of sea salt and some freshly ground black pepper. Drizzle about two teaspoons of the dressing over each plate of beef, leaving a couple of teaspoons in the bowl then toss the rocket in the remaining dressing and divide between the two plates. Scatter the parmesan shavings over the beef, and serve immediately.