In a pan, boil the broad beans for 2 minutes. Drain and remove the outer skins.
Meanwhile, in a separate pan, boil the runner beans for 8 minutes, adding the peas to the pan for the final 4 minutes. Drain both and leave to cool before tossing together with the sliced shallots.
For the dressing, put all the remaining ingredients in a glass jar, screw the lid on and shake to combine.
Drizzle over the salad and serve.
Cook's tip: If serving at a picnic, take along the dressing in the jar and dress the salad once you're there.