Rosti fish cakes - Good Food Middle East

Ingredients

• 300g potatoes
• 80g can tuna in brine, drained (or use salmon - see tip, below)
• 2 tbsp capers in brine, drained
• 2 spring onions, trimmed and finely chopped
• 1 large egg, beaten
• 4 tbsp olive oil
• ½ bunch asparagus spears, from Asparagus, pea & feta frittata - see 'goes well with')
• 1 tbsp lemon juice
• 1 tsp Dijon mustard
• ½ pack watercress