Rösti baskets with beef and salsa verde

Name: Rösti baskets with beef and salsa verde
Ingredients: 3 medium potatoes (600g), unpeeled; 30 gram butter, melted; 1 tablespoon olive oil; 1 small brown onion (80g), chopped finely; 1 clove garlic, crushed; 500 gram beef mince; 1 tablespoon plain (all-purpose) flour; 3/4 cup (180ml) beef stock; 1/3 cup fresh flat-leaf parsley, finely chopped; 2 tablespoon fresh basil, chopped finely; 1 tablespoon fresh mint, chopped finely; 1 teaspoon dijon mustard; 1 tablespoon red wine vinegar; 2 tablespoon olive oil; 1 tablespoon rinsed, drained capers, chopped finely