Cut broccoli into 1 1/2-inch florets. Peel stems, cut in half lengthwise, and cut into 1/2-inch-thick slices on the diagonal. Combine balsamic vinegar, garlic, olive oil, 1/2 teaspoon salt, and 1/4 teaspoon pepper in a bowl, whisking well. Add 1/2 teaspoon salt to a pot of boiling water. Add broccoli stems to pot and cook for 2 minutes. Add broccoli florets to pot and cook for another minute, or until bright green. Rinse and drain. Combine the broccoli, sun-dried tomatoes, pine nuts, and balsamic mixture; toss well. Sprinkle 1/4 teaspoon each of salt and pepper on salad; drizzle with Champagne vinegar.