Place the broccoli into a large pot with about 1 inch of water in the bottom. Bring to a boil, and cook for 7 minutes, or until tender but still crisp. Drain, and arrange broccoli on a serving platter.
While the broccoli is cooking, melt the butter in a small skillet over medium heat. Mix in the brown sugar, soy sauce, vinegar, pepper and garlic. Bring to a boil, then remove from the heat. Mix in the cashews, and pour the sauce over the broccoli. Serve immediately.