Roast Beef In The Clay Pot

• 6 onions (white peeled)
• 6 potatoes unpeeled (new)
• 2 bay leaves (whole)
• 1 arrowroot approximately
• 2,300 gr rolled roast of beef
• 5 gr parsley
• 6 slices carrots peel
• 6 slices mushrooms (sliced)