To prepare stew: Heat 2 teaspoons oil in a medium skillet over medium heat. Add sausages and cook until browned on all sides, 5 to 6 minutes. Transfer to a clean cutting board. Let cool slightly and cut into 1-inch pieces.

If using parsnips, quarter lengthwise and remove the woody core before dicing. Heat the remaining 2 teaspoons oil in a Dutch oven over medium heat. Cook onion, stirring occasionally, until barely tender, about 4 minutes. Add root vegetables and cook for 5 minutes. Add garlic and sage (or rosemary) and cook until fragrant, about 30 seconds. Add broth and bring to a simmer, stirring often.

To prepare dumplings: Meanwhile, whisk whole-wheat flour, cake flour, sage (or rosemary), baking powder and salt in a medium bowl. Add egg and milk and stir until a stiff batter forms.

When the stew reaches a simmer, stir in greens and the sausage and return to a simmer. Drop the dough, about 1 tablespoon at a time, over the stew, making about 18 dumplings. Adjust the heat to maintain a gentle simmer, cover and cook undisturbed until the dumplings are puffed, the vegetables are tender and the sausage is cooked through, about 10 minutes.

Beets, carrots and parsnips are easily peeled with a vegetable peeler, but for tougher-skinned roots like celeriac, rutabaga and turnips, removing the peel with a knife can be easier. Cut off one end of the root to create a flat surface to keep it steady on the cutting board. Follow the contour of the vegetable with your knife. If you use a vegetable peeler on the tougher roots, peel around each vegetable at least three times to ensure all the fibrous skin has been removed.