02Meanwhile, place the red onions in a bowl and cover with cold water. Soak 5 minutes, then drain and rinse. Dry on paper towels.
03Make the dressing. Mix together the lemon juice, vinegar, mustard, garlic, salt, and pepper. Whisk in the olive oil (or the oil and buttermilk or yogurt). Set aside.
04When the beans are tender, add the broccoli. Turn up the heat, cover and simmer or steam (depending on how much water is left in the pan) 5 minutes, until the broccoli is tender but still bright. Drain the beans and broccoli and toss with the dressing. Add the herbs and the Parmesan, toss again, and serve warm.