For best results, don't double this recipe. If the onions are packed too deeply in the slow cooker, they steam and stay pale and boiled tasting instead of caramelizing. They would eventually caramelize, but not before the beef would become dried out and overcooked.
A fresh tossed salad with a vinaigrette would taste great with this rich soup. Spoil your family with a small fancy French pastry from the bakery for dessert.
If you broil the soup with cheese on top, place the soup bowls on pretty plates to protect fingers and your table from the hot bowls.