Put the potatoes in a pan of boiling salted water, cook until soft, then drain.

Meanwhile, heat the oil and half the butter in a saucepan, add the onions and garlic, cover with a lid and cook until very soft but not coloured. Add the bacon and cook for 4 minutes. Turn off the heat and leave covered. Add the potatoes as soon as they are ready.

Put the beans in a saucepan of salted boiling water and cook for 2 minutes. Add the asparagus and cook for 1 minute. Add the broad beans and cook for 1 minute. Add the peas and cook for 1 more minute. (If the skins on the broad beans are too thick, cook them separately and pop them out of their skins.) Drain in a colander and refresh immediately under cold running water. This will stop them cooking further.

Meanwhile, put the saucepan with the potatoes over medium heat, add the remaining butter, the green vegetables and 2 tablespoons water. Mix gently and warm through with the lid on for a minute or so, then serve.