You are not going to believe how easy this is to make! And, it costs way less to make a whole pot of it than one bowl at a restaurant. I always make a GIANT pot of it and freeze part of it to enjoy later.
What you will need:
4 large onions
2 tbs. butter
2 tbs. sugar
4 tbs. flour
1 envelope of onion soup mix
1 tsp. salt
4 tbs. paprika
4-6 cups water (or you can use vegetable stock to give richer flavor)
1 package mozzarella cheese
Any leftover bread
In a large pot, melt the butter on medium heat. While the butter is melting, slice up 4 large onions. Once the butter is melted, add the onions to the pot. Let the onions sweat for 15-20 minutes, stirring occasionally. I add the sugar halfway through.
Once the onions have a nice brown sheen to them add the flour, onion soup mix, salt, and paprika. Stir the mixture until it’s all incorporated and is a thick paste consistency.
Slowly add the water. I start with ½ cup at first so that the water mixes with the thick paste mixture. Once the water mixes completely, I add the remaining cups of water and stir it all together. 
Let the soup simmer on medium heat for an hour with the lid propped on top, but slightly open to let steam out. 
While the soup is making, cut any bread you have up into medium size squares. Sprinkle some paprika on the top. Toast on 350°F for 10 minutes.
Once the soup is ready, it’s time to assemble it in the bowls! I love using these little handled crocks like they do in the restaurants to get the full effect! Ladle the soup into your bowls; sprinkle some mozzarella cheese, then a layer of croutons, and finally another {heaping} layer of cheese. Bake in the oven at 350°F until the cheese bubbles and turns brown.
I let the remainder of the soup cool down, then I pour into freezer safe containers to enjoy when I just don't feel like cooking. They can last months in the freezer like this.
Enjoy! 
