Amy Riolo: Nothing beats a piping hot bowl of French onion soup in the winter. This classic restaurant version is very easy to make. Let's begin. Melt a quarter cup of butter in our saucepan. Now that our butter is melted, we can add two sliced red onions and two sweet onions or yellow onions. Just stir these really well to coat them in the butter. Now, I will turn my fire down to low and I will let these continue to saut for about 20 minutes. So now that the onions are finished sauting, they are nice and cooked down and they have a really syrupy consistency, we can go ahead and add in our stock. Then I could add in our parsley. I am also going to add in a sprig of thyme, and a bay leaf, and we will just bring this up to a boil. So now that our soup is boiling, we can just reduce our heat to low and cover it. So 20 minutes have passed and our French onion soup has really thickened. Now we can just remove our thyme and our bay leaf and I am going to add in the two tablespoons of balsamic vinegar. I am also going to add in a little bit of salt and pepper. The saltiness of your stock will let you know how much you need. And now we can ladle our soup right into the ramekins. We can put one of our pieces of toasted bread right on top in the middle of each one. I can top each one with two slices of Gruyre cheese, take our mozzarella and just sprinkle a little bit on top of each one. And I have my broiler preheated. This will take just a couple of minutes for the cheese to melt. Here we have our French onion soup, the perfect prelude to a winter meal. Enjoy!