Dab fillet dry, place in a freezer bag and freeze for 20-30 minutes (this makes it easier to cut into thin slices).
For the mayonnaise, mix mustard powder with 2 teaspoons of cold water. Leave to stand for approx. 10 minutes to allow the aroma to fully develop. Chop the capers. Mix the egg yolks and mustard briefly in a bowl with the whisk of the mixer.
Stir in about 1⁄3 of the oil drop by drop until oil and egg yolk have combined to form a smooth cream. Then slowly add the remaining oil in a thin stream, stirring continuously, and continue to whip until a thick, creamy mayonnaise is obtained.
Finally, stir in wine and capers. Season to taste with salt and pepper.
Cut the fillet into wafer-thin slices. If they are not thin enough, place the slices of meat between a cut open freezer bag and beat them wafer-thin with a pan bottom or flat iron.
Completely line four plates with fillet slices. Pour the mayonnaise into a disposable piping bag, cut off the tip and spray as a grid on the fillet. Add the rest. Season carpaccio with coarse pepper.
Ciabatta goes with it.