Bennigan's Potato Soup

• 1 potato (diced)
• 1 parsley for (chopped garnish)
• 550 gr chicken base
• 240 ml milk
• 85 gr margarine divided
• 55 gr onion (yellow diced)
• 40 gr margarine
• 22 gr flour
• 45 ml margarine in a stockpot
• 14 gr ham base