For the filling,

In a medium pot, whisk the orange juice with the eggs until blended, about 2 minutes. Add the grated orange peel and sugar. Set over medium heat, stir well. Add the butter cut into small pieces, cook in a double boiler until thickened, about 20 minutes. Add the dissolved cornstarch, if need it, and cook one more minute. Allow cooling before assembling the cake. Keep refrigerated.

For the cake,

1. Preheat the oven, turn on the grill, no fan. You will use the broiler for cooking the crepes. Place the oven rack in the middle position.
2. Prepare a cake mold with high sides (I used an 8×3″). Butter very well and put parchment paper at the bottom.
3. In a bowl, beat butter and sugar until it is creamy, about 5 minutes. Keep beating on low speed, adding the yolks one at a time, beating until fully incorporated in between.
4. In another bowl with very clean beaters, beat the egg whites with a pinch of salt until stiff, do not overbeat because they will dry up.
5. In a large bowl, mix the two batters with light movements.
   
6. Working with a wooden spoon or spatula (do not use a whisk), add the sifted flour and incorporate gently.
   
7. Pour 1/2 cup of batter into the buttered pan and spread with a spoon or spatula across the bottom. Cook for 1 minute and a half to 2 minutes until lightly golden. You can open the oven and look.
8. Remove and cover with three tablespoons orange filling, spread.
9. Add 1/2 cup of the batter on top of the filling and spread gently. Bake the second crepe in the same way.
10. Continue cooking until you have no more batter, and always alternate filling and crepe batter.
11. Let cool entirely on a rack.
    
12. Unmold cool (I refrigerated the cake in the pan for at least 2 hours), cover with the orange filling left.
13. Refrigerate until ready to serve. Taste better after a night on the fridge.