To make a good salad is to be a brilliant diplomatist -- the problem is entirely the same in both cases. To know exactly how much oil one must put with one's vinegar.
Lightly fry the meat in a large frying pan in the oil and butter until the surface browns. Add onion and leave on heat so that the onion turns transparent, adding a little white wine every so often to prevent the onion from frying.
To prevent the sauce from burning add a few tablespoons of water now and then.* Peel the potatoes and cut into bite sized pieces. Add the potatoes, the rosemary and the garlic to the frying pan and add water to cover. Continue cooking for another 30 minutes.
*The water must cover the potatoes! **The potatoes are done when you can easily stick a fork in them.