Goulash with mashed potatoes

Goulash like in a canteen in Soviet times

INGREDIENTS:
• meat - 500 grams
• onion - 1 piece
• tomato paste - 2 tablespoons
• flour - 2 tablespoons
• cold water - 300 milliliters
• salt
• pepper
• sugar
• potatoes - 1 kilogram
• butter - 50 grams
• milk - 50-100 milligrams
• parsley