Beef with Mustard Sauce

For the roast: Break the cauliflower and broccoli into florets. Blanch the carrots, zucchini, celery root and kohlrabi. Remove the cherry tomatoes from the stems.

Blanch the vegetables in the beef broth. Remove and keep warm.

Season the beef with salt and pepper. Cook all over in butter.  Tie with kitchen string and hang on a wooden spoon so that the meat can be submerged in the broth without touching the wall or bottom of the pot. Simmer in the broth about 30 minutes to poach.

For the mustard sauce: Mix the yolks with the Creme fraiche. Move approximately 125 ml (approximately 1/2 cup) of the broth to a mixing bowl. Whip the cold pieces of butter with a hand blender little by little with the broth until a creamy sauce is achieved. Pour the sauce back into the pan and heat, but do not boil. Stir in the crème fraîche mixture. Add the mustard and whipped cream. Season the sauce with lemon juice, sugar, salt and pepper. Keep warm.

Heat the vegetables in the broth. Cut the tenderloin into slices and serve.