Crunchy Tuna Casserole

Ingredients

• 30 g butter
• 1 onion, finely chopped
• 400 g can condensed cream of mushroom soup
• 2 hard boiled eggs, shelled and chopped
• 250 ml frozen peas
• 200 g can of tuna, drained and flaked
• 30 g packet of cheese and onion potato crisps, crushed
• salt and pepper to taste