Wash and scrape carrots and run through juicer. Discard pulp, or reserve for another use. Pour juice into small, low-sided skillet or saute pan, whisk over medium heat until bubbling at edges. Add slurry and cook, whisking to desired consistency; don't cook too long. Whisk in brandy; remove from heat. Whisk in chopped green onion. If using, whisk in butter until blended; serve. Makes 1 1/2-2 cups.