Roast Beef with Mustard Crust and Potatoes

For the roast: peel carrots, parsnips and onions. Chop everything coarsely. Rinse tomatoes, remove stalks and cut into pieces.

Rinse and pat dry meat. Season with salt and pepper, tie with a kitchen string. Heat butter in a roasting pan and brown meat on all sides. Remove from the pan and saute vegetables (except tomatoes) in the same pan briefly. Deglaze pan with wine and add broth, bay leaf and  tomatoes. Return meat to the pan. 

Whisk mustard with sour cream and egg yolk and season with pepper. Spread mixture on meat. Roast in preheated oven at 160°C (approximately 325°F) for about 2 hours and 30 minutes, add water as needed to the pan. 

For the potatoes: peel potatoes and cut into bite-sized pieces. Heat clarified butter in a pan and cook potatoes until golden brown, turning. Season with salt, pepper and cumin powder.