Buttery Root Vegetable Ragout

Name: Buttery Root Vegetable Ragout
Ingredients: 4 tablespoons unsalted butter; 1 large white onion, coarsely chopped; 2 large garlic cloves, minced; 1/2 small butternut squash, peeled and cut into 1/2-inch pieces (1 1/2 cups); 2 medium carrots, sliced 1/2 inch thick; 1 small parsnip, sliced 1/2 inch thick; 1 medium Yukon Gold potato, peeled and cut into 1/2-inch pieces; 2 cups shredded Savoy cabbage; 1 1/2 cups vegetable stock; 1/4 cup dry white wine; Salt and freshly ground pepper; 1 tablespoon chopped flat-leaf parsley; 1 tablespoon snipped chives; Couscous, for serving