**Make the Crepe Batter:**
In a blender, combine all the ingredients for the crepes. Blend until smooth and free of lumps. Refrigerate the batter for at least an hour.
**Cook the Crepes:**
Heat a non-stick pan over medium-low heat. Brush the pan lightly with melted butter, then pour in just enough batter to coat the pan in a thin layer. Cook for about 2 minutes until the edges start to turn golden. Flip and cook for another minute on the other side. Repeat until all the batter is used. You should have 20-30 crepes. Let them cool on a rack.
**Prepare the Diplomat Cream:**
In a saucepan, heat the half and half with sugar until warm. In a separate bowl, whisk together egg yolks and cornstarch. Slowly pour the warm milk mixture into the egg mixture, whisking constantly. Return the mixture to the pan and cook over medium heat until thickened. Stir in the vanilla, rose water, and butter. Let the cream cool completely.
**Assemble the Cake:**
Place the first crepe on a serving platter and spread a thin layer of diplomat cream. Continue layering the crepes with cream in between each layer, gently pressing down after each addition. Chill the cake for 15 minutes to set the layers.
**Decorate and Serve:**
For decoration, you can top the cake with fresh berries, chocolate ganache, or a light dusting of powdered sugar. Chill for at least an hour before serving for neat slices.