To prepare the whiskey sauce -a task that we can do the day before- we finely chop the shallot and fry it in the butter, always over low heat. stirring for ten minutes to avoid burning the butter. Add a tablespoon of flour and stir with the help of a few rods, for a couple of minutes.
It is time to add the whiskey, turn up the heat so that it evaporates completely and then add the broth. We stir with the rods, rectify the salt and pepper and we let reduce until it has the right consistency. We keep it in a jar in the fridge until we are ready to use it. To heat it we can do it in a double boiler while the meat is cooked the day we are going to serve it.
To make the beef tenderloin, which we will have removed from the refrigerator at least an hour before cooking, We mark the meat over very high heat in a pan, preferably iron, leaving it on one side for three minutes, without touching or squeezing it, and then on the other side for another three minutes, if you like your meat undercooked. To make it to the point, it will take 4 minutes for each side.
With that, it is enough to get a meat that is golden on the outside, juicy and reddish on the inside, and really tender. Carve the meat into slices approximately one cm thick and we place them in a source mounted one on top of the other.
Finally, we finish the recipe by covering the meat portions with a little sauce and decorating with salt flakes and pepper to taste. We serve the beef tenderloin on the platter with its garnishes on one side of the platter and more sauce for whoever wants it, in a separate bowl.