Cut sausage into 1-inch (2.5 cm) pieces. In large saucepan, heat oil over medium-high heat; brown sausage. Transfer to bowl. Drain fat from pan.
Add onion, garlic, potatoes, Italian herb seasoning, pepper and hot pepper flakes to pan; fry over medium heat, stirring occasionally, until onion is softened, about 5 minutes.
Add water and stock; bring to boil. Return sausage to pan; reduce heat, cover and simmer until potatoes are almost tender, about 7 minutes.
Add Swiss chard; simmer, covered, until tender, about 5 minutes. Top with Parmesan cheese.
