Preheat oven to 425°F (220°C). Place Brussels sprouts in bowl and toss with vinegar, garlic, salt and pepper. Place in a baking pan and add 4 tablespoons of water or vegetable broth and cover. Cook for 10 minutes and uncover. Continue to cook for 20-30 more minutes or until they begin to brown and are tender. Add more water or vegetable broth if sprouts begin to get too brown before they are done. When tender, remove from oven and toss with walnuts and croutons. A little olive oil can be added to the toss, but is hardly necessary.