Step 1Blanch the parsnips in boiling salted water 1 to 2 minutes. Remove them from the water with a slotted spoon. Reserve the water.
Step 2Trim the lower third of the asparagus spears. Bring the water back to a boil; blanch the asparagus 1 minute. Remove from the water with a slotted spoon.
Step 3Trim the tops and root ends from the baby onions to make 3- to 4-inch pieces. Blanch them in the same boiling water for 30 seconds and remove.
Step 4Heat the butter in a large skillet over medium-low heat. Add the blanched parsnips, asparagus and onions. Season with salt and pepper and cook 2 to 3 minutes, stirring occasionally.
Step 5Add the water and simmer over medium-low heat until the vegetables are tender, about 5 minutes.
Step 6Stir in the lemon juice and chives, if using, and serve.