I know it may seem a little crazy to use the slow cooker when you have to transfer it to a bowl to add the bread and melt the cheese and on top and use a skillet to caramelize the onions. But, trust me, the soup is so flavorful after 9 hours in the slow cooker. Cooking it low and slow really lets the flavors develop and gives it a richness that you wouldn't get from a stovetop soup, unless it was on the stovetop for hours and nobody has time to man the stove that long. You can see if your slow cooker has a sauté option which may help eliminate the need to sauté the onions on the stove first.