French Dip Beef Sandwich

With leftover roast beef I made and unbelievably messy, fall apart french dip sandwich! 

1. Saute an onion in a little bit of olive oil
2. Cut up and shred roast beef
3. Add in a cup of water and let simmer and shed even more
4. Make a creamy, low fat sauce with FF Greek yogurt, horseradish and S & P
5. Toast buns in oven with garlic powder and shredded mozzarella cheese
6. Pile high and soak with beef broth (I used left over broth from a brisket dinner that I had in the freezer)
7. Grab a couple napkins and dig in!!!!!