Beef Wellington and mashed potatoes

Ingredients Beef Wellingtion 1Kg of Beef tenderloin Salt according to your tastes or 12gr Pepper according to your tastes or 3gr 800gr Fresh whole mushrooms 1 head of garlic 1 bunch of Parsley 1 roll of puff pastry 2 egg yolks 20cl of milk Mashed potatoes 1 Kg of...