1cupmelted unsalted butter, plus more to grease the pan
3large egg yolks
1/2teaspoonkosher or coarse sea salt, or to taste
For the chocolate pastry cream:
4cupswhole milk, divided
1cupgranulated sugar, divided
6large egg yolks
8ounces (or 1 cup)dark or semi-sweet chocolate, finely chopped
For the chocolate ganache:
1/2cupheavy whipping cream
4ouncesbittersweet chocolate, chopped
2tablespoonsconfectioners' sugar, for dusting
To make the crepes:
In a small saucepan, heat the butter over low heat until it melts.
Place the flour, eggs, egg yolks, milk, sugar, salt and melted butter in the blender and purée until smooth, about 10 seconds. Add the water and blend again until smooth. You can also mix the ingredients by hand, following the same order.
Place the batter in a container, cover and refrigerate for at least half an hour, or up to 12 hours. Once ready to make the crepes, whisk the batter well with a fork or a whisk.
Set a crepe pan or 7 1/2- to 8-inch nonstick skillet over medium-high heat for a couple of minutes. Butter the bottom of the pan and ladle about 1/4 cup of batter into it. Instead of working from the center to the sides, tilt the pan and pour the batter over one side and spread it as quickly as possible to the rest of the pan, so that it covers the entire surface.
Cook for about 25 seconds, until edges are cooked and begin to dry out and the bottom of the crepe is lightly browned. With a small spatula or fork, lift one edge of the crepe and turn it over quickly with your fingers. Cook the second side for about 15 seconds, or until it has lightly browned. Flip the crepe onto a plate.
Repeat with the rest of the batter. After 3 or 4 crepes, you may need to butter the pan again. If it isn’t a nonstick pan, you may need to do it for each one. Stack the crepes on top of each other with the first/darker side down. You should have about 35 to 40 crepes.
To make the chocolate pastry cream:
In a small bowl, mix together the cornstarch and 2/3 cup of the milk. Using your fingers might be easiest. This creates a slurry to prevent lumps in your cream.
In a large pot over medium-high heat, bring the remaining milk, cream and 1/2 cup of the sugar to a simmer. In a medium bowl, whisk together the remaining 1/2 cup sugar and the egg yolks.
Ladle 1/2 cup of the simmering milk mixture into the eggs, whisking into the eggs while you pour in order to temper the eggs, so they won’t curdle. Once completely combined, pour the egg mixture into the pot with the milk mixture and add your cornstarch slurry. Stirring frequently, cook until mixture is thickened. Remove from the heat, stir in the butter, vanilla and chocolate, until it is all melted and combined. Set aside to cool until ready to use. If it will be more than a few hours, cover with plastic wrap and refrigerate until ready to use.
On a cake stand or serving platter, place a crepe and spread or pipe about 3 tablespoons of pastry cream onto the crepe. Repeat until all the crepes and cream are used up. Refrigerate the cake for at least 8 hours or overnight.
To make the chocolate ganache (make this after the cake has been refrigerated):
Place the chopped chocolate in a large heat-proof bowl. In a small saucepan, bring 1/2 cup cream to a boil. Pour the hot cream over the chocolate. Let it sit for 5 minutes undisturbed, then fold with a rubber spatula until the chocolate and cream are mixed completely.
Pour ganache onto the top of the refrigerated cake, letting it drip slightly down the sides. If desired, top with a dusting of confectioners’ sugar and serve with sliced strawberries.