First, prepare the Keto Phyllo dough. Using an electric mixer, beat 6 eggs, 4 egg whites, sea salt, nutmeg and cinnamon for 5 minutes. Start slowly adding melted butter. Keep mixing.
Now add psyllium powder and mix until it's unified. Replace the wire whip with a dough mixing hook. Start adding almond and coconut flour. Keep mixing for another 5 minutes. The dough will thicken.
Wrap the dough in plastic foil and place it in the refrigerator. Let it rest for 1 hour.
Prepare the filling. Place mascarpone, sweetener, salt, vanilla extract and orange zest in a deep saucepan. Now add egg yolks. Place the pot on the stove and start heating the mixture at low temperature while whisking it energetically. When it bubbles and boils, remove it from heat. Set it aside and let it cool down totally. You can place it in another bowl and place it in the refrigerator to cool down quicker.
After the dough was chilled for 1 hour, place it in between two parchment papers. Gently and slowly roll it and make it approximately 5mm thin. If you are feeling brave, try even thinner. Try to get 50x50 cm (20x20 inch) square.
Place the filling which you previously chilled in the refrigerator in the middle creating 25x25 cm square. Flip the sides of the dough to cover filling from all sides. You can use some melted butter to wash the dough and prepare it for baking.
Place the Bougatsa together with the lower parchment paper on a wide baking sheet. Bake the Bougatsa at 180ºC (350ºF) for 30 to 35 minutes.
Remove the bougatsa from the oven and place it on the wide plate. It should not stick to the parchment paper and you can use heat resistant gloves to move it. Sprinkle with Ceylon cinnamon and powdered stevia.