Bring a pan of water to the boil, add the broad beans and bring back to the boil, then cook for one minute. Drain the beans and run them under cold water to cool, then remove their greyish skins and set aside.
Melt 25g of the butter with the tablespoon of oil in a large pan and fry the onion for a few minutes until softened, but not coloured. Add the garlic and cook for another couple of minutes, then stir in the thyme, lemon zest, bay leaf and rice and cook for a few seconds longer until the rice is glistening.
Pour the wine into the pan and cook over a medium heat until the liquid has reduced by half. Slowly start adding the stock, a ladleful at a time, stirring well in between each addition. Simmer for two to three minutes or until the liquid has almost all been absorbed before adding more. Continue to cook and add stock for 15 minutes or until the rice is tender.
Meanwhile, bring a separate pan of water to the boil. Add the runner beans and cook them for three minutes, or until tender. Drain, then tip the beans back into the pan and toss with a small knob of butter and plenty of pepper.
Remove the thyme and lemon zest from the rice and discard. Stir in the broad beans, peas and asparagus with the remaining stock and cook for 3 minutes until tender, stirring regularly. Remove from the heat and stir in the feta. Season with salt and pepper, then cover with a lid and set aside for a few moments.
Add the remaining butter to the risotto and stir. Serve, topped with some runner beans, minted olive oil and shavings of Parmesan, if using.