Prepare the brussel sprouts by removing any yellowed outer leaves, trimming off the root end and cutting them in half lengthwise. Place them in a large mixing bowl, making sure to collect any leaves that have come loose from the sprouts.
Douse the sprouts with olive oil and mix very well, making sure every spout is well coated and massaging so that outer leaves come free. Move sprouts to a parchment lined baking sheet sprinkle generously with garlic powder and salt.
Transfer to oven and roast for 20 minutes. Remove from oven and toss. Return to oven 10 to 20 minutes longer. Watch them carefully. When the hearts of the sprouts are tender and the outer leaves are dark and crispy, they're done.
In a separate bowl whisk together all the ingredients for the sauce. Pour over the sprouts when they come out of the oven, and serve immediately.