In a large nonstick skillet, heat oil over medium-high heat. Add onion, and cook, stirring occasionally, 2 minutes. Add garlic, and cook 2 minutes more. Add escarole, and stir slowly, allowing it to wilt slightly. Add chicken stock, thyme, and salt; reduce heat to medium-low. Simmer for 15 minutes. Stir in the beans, and continue to simmer until most of the liquid is absorbed and the greens are tender, 3 to 5 minutes. Remove from heat. Serve warm, garnished with grated Parmesan cheese.