Slice the onion and toss in the lemon juice to coat all the slices - set aside.
In a large frying pan, heat the oil over a moderate heat until hot.
Add the pine nuts and garlic and fry for 20-30 seconds before adding the broccoli. Stir fry the broccoli for 1-2 minutes before adding the wine and letting it sizzle for 30 seconds to burn off the alcohol. Add around 1/2 cup water and put on a lid.
Let the broccoli cook for 2 minutes then remove the lid and reduce until all the liquid has evaporated. Season well with salt & pepper.
Remove from the heat and then stir in the mint and tip onto a serving dish. Scatter over the onions and serve.