I typically try to minimize the amount of dirty dishes I create so I boil and sauté in the same pot, I would choose one that is a little bigger than you might think so you have room for the sauté.

3-4 pieces Scorzonera, peeled and sliced
1 Tbs butter or olive oil
1/2 cup onion diced
3/4 cup fava beans, shucked and peeled
Salt and Pepper

Immediately after slicing the scorzonera place into a sauce pan with 3 cups cold water to keep from browning. Add a 1/2 teaspoon salt and bring to a boil, cooking for 5-7 minutes, until tender. If your fava beans are raw, add them to the boiling water for the last 2 minutes. Drain the water and add the butter and onion cook over med-high heat until the onion is translucent, about 2-3 minutes, season with salt and pepper.