1. Preheat oven to 365 Degrees Fahrenheit.
2. For the potato Au Gratin: Grease a baking tray and layer with potatoes.
3. Add 1/2 cup parmesan cheese and 1/2 cup mozzarella.
4. Add a pinch of garlic, dry garlic, salt and pepper.
5. Repeat the same layers starting from potatoes till the baking tray is full.
6. Pop into the oven at 365 degrees Fahrenheit.
7. Check every 20 minutes and cook for an hour and a half.
8. For the filet mignon: Season the filet mignon with salt and pepper.
9. Grill to medium rare or to your preference.
10. For the Demi Glaze Sauce: In a pan, heat the short rib stock and shallots.
11. Reduce the sauce and add red wine and simmer.
12. Add butter and stir and reduce.