Place butter in large pot. Add garlic and saute until nice and toasty. Add onions (which have already been caramelized). Add flour. Cook for 5 to 10 minutes.
Deglaze the pot with brandy, making sure all of the flour is mixed in. Bunch thyme, bay leaf, and black peppercorn in a cheesecloth or sachet and add to pot. Pour in veal stock. Simmer on low for 2 hours.
Once soup is done, scoop into individual bowls that will withstand the heat of the oven. Top each bowl with a slice of brioche and then a slice of comté. Place under broiler until cheese is golden brown.