Grandma's Warm Potato Salad

This is my grandmother's recipe for warm potato salad. It's a sweet and sour side dish which goes great with pork, sausages. Simple to make and a good everyday dish, but not sure why she calls it a salad, though.

Ingredients:
Potatoes (as many as you'd normally make, depending on how many you are)
1 onion
1 tbsp butter
1 tbsp sugar
1 tbsp vinegar
Salt and pepper

Start by boiling the potatoes. Better a bit overcooked than undercooked.

Meanwhile, slice the onion finely and fry the in the butter with some salt until they start going translucent. Then add a cup of water and the sugar. Let it simmer 10 minutes.

By then the potatoes should be about done. Drain the water, slice or cut them into chunks. Add them to the onions and stir. The starch will thicken the liquid. Add the vinegar, pepper and taste for salt. You might want to add extra vinegar according to taste.
Serve warm.