To make the crumbed brains, clean the brains under cold running water, then place in a saucepan and cover with cold water.
Add the onion, celery, bay leaves and salt and bring place onto a slow to moderate heat and bring to the boil, simmer gently for 2 minutes. Remove from the heat and allow the brains to cool in the poaching liquid until needed.
Place the eggs and milk in a bowl and whisk to combine. Spread out the flour and breadcrumbs on separate trays.
Carefully remove the brains from the poaching liquid with a slotted spoon and drain on paper towel. Separate the two lobes by cutting each in half and removing some of the middle bits.
Working in small batches, place the lobes in the flour and roll to cover, then place into the egg wash to coat, draining off any excess. Finally, roll the brains in the breadcrumbs until well coated.
Pour the vegetable oil into a wide-based saucepan and heat over medium heat. Add the brains in batches and cook for about 3 minutes or until golden and crunchy. Remove with a slotted spoon and drain on paper towel. Season with sea salt.
Meanwhile, heat the olive oil and butter in a frying pan over medium heat and allow the butter to melt and start to foam. Add the spinach and toss until wilted, then add the pine nuts and lemon juice, and season with salt and pepper. Mix to combine.
Place the spinach mixture on plates and drizzle with some of the cooking juices. Top with the crumbed brains and serve.