Blend all spice paste ingredients in a food processor until smooth.
Marinate fish fillets in lemon juice and salt for five minutes.
Pat fish dry and marinate in the green spice paste for 40 minutes.
Heat vegetable oil in a pan over medium-high heat.
Scrape excess marinade from fish and fry skin-side down for one minute.
Turn fillets and fry for two minutes until cooked through.
Add butter, baste fish with juices, and drain on kitchen paper.
Heat olive oil in a small pan and soften red onions for two minutes.
Fry coriander, cumin, and sesame seeds for one minute.
Add apple batons, lime juice, and curry powder and cook for one minute.
Stir in mango chutney and mayonnaise then remove from heat.
Sprinkle with mint and serve fish over the salad garnished with cress.