| 1. | Preheat the oven to 400°. |
| 2. | Toast your bread in the oven on a cookie sheet - 5 minutes on the first side, then 2 minutes on the opposite side. Set aside. |
| 3. | In a small saucepan set over low heat, melt the butter and then add the flour, stirring constantly with a wooden spoon for ~2 minutes. |
| 4. | Slowly pour the warm milk into the pan with the butter/flour mixture and cook, whisking constantly, until the sauce is thickened, about 3 - 5 minutes. |
| 5. | Remove from heat and add the salt, pepper, nutmeg and stir. |
| 6. | Add in 1/4 c of the Gruyere, 1/4 c of the Emmentaler and all of the Parmesan and stir until cheese has all melted. Set aside. |
| 7. | Spread dijon mustard on all of the bread. |
| 8. | On half of the bread, lay out tomatoes on a single layer. |
| 9. | If desired, add a couple of slices of ham on top of the tomatoes. (croque monsieur) |
| 10. | Top the same slices with the remaining Gruyere and Emmentaler, about 1/3 of the total cheese on each. |
| 11. | Top each 'loaded' slice with one of the dijon-only pieces of bread. |
| 12. | Top each sandwich with about 1/3 of the bechamel (cheese sauce) |
| 13. | Bake the sandwiches for 5 minutes. |
| 14. | Switch your oven to broiler and broil for 3 to 5 minutes (depending on how close your heating element is to your sandwiches) or until the topping is bubbly and lightly browned. |
| 15. | Serve hot. |