MAKE THE BISCUITS: Preheat the oven to 375°. In a large bowl, whisk the all-purpose and cake flours with the sugar, baking powder and salt. Using a pastry blender or 2 knives, cut in the cold butter until it is the size of small peas. Stir in the cream until a shaggy dough forms.
Turn the dough out onto a very lightly floured surface and knead 2 or 3 times, just until it comes together. Roll the dough into a 7-inch round, about 3/4 inch thick. Using a 2 3/4-inch or 3-inch biscuit cutter, stamp out 5 biscuits. Gently gather the scraps and reroll them; cut out 1 more round so you have a total of 6 biscuits.
Transfer the biscuits to a baking sheet and brush with the melted butter. Sprinkle the turbinado sugar on top and bake for 25 to 30 minutes, until the biscuits are golden. Let cool.
MEANWHILE, MAKE THE LEMON CREAM: Set a strainer over a medium bowl. In a small saucepan, combine half of the lemon zest with the lemon juice, sugar, egg, egg yolk, salt and 1 tablespoon of the butter. Cook over moderate heat, whisking constantly, until thickened, about 5 minutes. Immediately strain the curd into the bowl. Whisk in the remaining lemon zest and 2 tablespoons of butter. Press plastic wrap directly onto the surface and refrigerate until cool, about 15 minutes.
In a medium bowl, softly whip the cream. Fold the lemon curd into the whipped cream and refrigerate for at least 15 minutes.
PREPARE THE STRAWBERRIES: In a medium bowl, toss the strawberries with the sugar and let stand for 15 minutes.
Split the biscuits in half and arrange the bottom halves on plates. Mound the lemon cream on the biscuits, top with the strawberries and their juices and replace the tops. Serve right away.