Bring a large pan of water to the boil and cook the broad beans for about 5 minutes or until just cooked. Drain into a sieve and cool under cold water. When cool enough to handle, slip the beans from their skins. Keep to one side.
Pour the stock into a pan and place onto a gentle heat until just warm, but not boiling. Heat the oil in a large pan, add the onion and cook until softened but not coloured. Add the bacon and cook until it is just beginning to colour.
Add the white wine and cook for 1 minute. Add the butter and leave until just melted. Add the rice and stir until glistening and coated in butter.
Add the stock, a ladle at a time, stirring gently after each addition. When the stock has been absorbed by the rice, add another ladleful. Continue to do this until most of the stock has been used and the rice is almost cooked but still has a bite. Add the crème fraîche or cream, Parmesan and lemon zest.
Remove and stir in the mint and beans. Check the seasoning one more time before you serve.