1. In a small sauce pot, heat Butter until melted then stir in Flour and cook until lightly browned and fragrant.
2. Slowly whisk in Milk, Parmesan and Mace and heat while stirring until cheese is melted and sauce simmers. Simmer and continue mixing occasionally for 2 to 3 minutes then turn off heat and set aside.
3. In a lightly oiled (or non-stick) frying pan cook an Egg sunny side up and set aside the Egg.
4. Spread Mustard and Mayonnaise onto the Toasted Brioche and generously layer Mortadella on top in folded layers to keep the sandwich fluffy.
5. Cover the Mortadella with Mozzarella and melt it under a broiler or with a torch then cover with another slice of Toasted Brioche.
6. Top the sandwich off with a generous helping of Parmesan sauce to cover the top, then lay the Sunny Side Up Egg over the sauce and garnish with some chopped Pistachios.
TIP: Eat quickly after adding the sauce so the sandwich does not get soggy!