Using a very sharp knife, finely chop the shallots and capers.
Dice the beef and then mix in the shallots and capers. Set aside at room temperature.
To make the dressing, whisk all of the ingredients together and using a rubber spatula, mix 150ml of it into the beef mixture with the sea salt and Espelette pepper.
Place a cooking ring on each serving plate and divide the beef mixture among them.
Put the egg yolks in a heatproof bowl set over a pan of simmering water that is approximately 60 degrees with 100ml of the dressing and lightly whisk to an emulsion.
Make a light hollow in the centre of each steak tartare and then carefully spoon in the egg yolk emulsion.
Add some Melba toast and watercress to each plate to serve.
