Heat a dry frying pan over a medium heat, then add the seeds and toast, shaking frequently, until lightly browned and fragrant. Set the seeds aside and return the empty pan to the heat.
Heat the butter and oil, then add the butter beans and asparagus and fry for a few minutes until the beans begin to turn crispy. Add the garlic and chilli flakes and cook for a further minute. Transfer it all to a bowl and set aside.
Add the spinach to the pan and allow to wilt slightly. Return the beans and asparagus to the pan with the spinach and heat through for a minute or so.
Serve topped with the spring onions, radishes, toasted seeds, chopped mint and a squeeze of lemon juice. Season with a little salt and pepper.