3 eggs, separated
1/2 cup sugar
3/4 cup all-purpose flour
1 cup orange juice (for soaking syrup)
1/2 cup sugar (for soaking syrup)
1 1/2 cups sugar (for optional caramel sauce)
3/4 cup water (for optional caramel sauce)
1 3/4 cup heavy cream, plus more for serving (for optional caramel sauce)
2 tbsp cornstarch (for buttercream and strawberry fillings)
1 cup milk (for buttercream and strawberry fillings)
1 cup (2 sticks) unsalted butter, softened (for buttercream and strawberry fillings)
2 quarts strawberries, washed (for buttercream and strawberry fillings)
1/4 cup plus 2 tbsp sugar (for buttercream and strawberry fillings)
1 tsp vanilla extract (for buttercream and strawberry fillings)
2 egg yolks (for buttercream and strawberry fillings)
Preheat the oven to 350 degrees fahrenheit.
Place the egg whites in the bowl of a stand mixer fitted with the whisk attachment and whisk on high for about 1 minute, until the whites are foamy
Add the sugar 1 tablespoon at a time until stiff peaks have formed, 5 to 7 minutes
Stir the egg yolks together in a small bowl. Add the egg yolks and the flour to the beaten egg whites and whisk on low speed for a few seconds.
Remove the bowl from the mixer and finish incorporating the ingredients with a rubber spatula until well blended.
Place an 8-by-2½-inch cake ring or a springform pan without the bottom on a sheet pan lined with Silpat or parchment.
Pour the batter into the ring and bake for 25 minutes, until the cake is lightly brown or a cake tester inserted in the center comes out clean.
Cool the cake in the pan for at least 1 hour or up to overnight. (This cake can be done a day before, or you can use a frozen, defrosted cake that you have baked in advance).
Meanwhile, make the soaking syrup by bringing the orange juice and sugar to a boil in a medium saucepan. Cook the syrup for 1 minute, then remove it from the heat and let cool.
Start the cream filling by whisking 1/4 cup of the sugar with the vanilla, egg yolks, cornstarch, and milk in a small microwave-safe bowl. Cook for 3 minutes on high, whisking vigorously halfway through and again at the end of cooking.
Cover the bowl with plastic wrap, placing the wrap directly on the surface of the filling to prevent a skin from forming, and refrigerate for at least 1 hour.
Choose 8 large strawberries that are about the same shape and cut them in half.
Place the cut sides down and trim them at the stem end so that the strawberries are all uniform in size.
Cut a 1/4-inch slice from the flat inside surface of each of the strawberry halves and set the slices aside for decoration. Reserve the remaining strawberry pieces separately.
Run the blade of a thin knife around the inside of the cake ring to separate it from the cake or open the latch of the spring-form pan. Using a serrated knife, carefully slice the cake horizontally into equal layers. Set aside.
Wash and dry the cake ring.
Cut two pieces of parchment and place them under the cake ring on a serving plate, letting them overlap in the center of the ring. (This helps you keep the plate clean).
Place the top piece of cake into the ring, cut side up. Spoon half of the soaking liquid onto the cake.
Press the strawberry slices, standing upright with the points at the top, around the inside of the cake ring.
Trim and chop the remaining whole strawberries and the reserved berry pieces and place them in a bowl with the remaining 2 tablespoons sugar. Stir to coat and set aside.
To finish the buttercream, whisk the cooled pastry cream vigorously by hand, or in a stand mixer fitted with a whisk attachment.
Cut up the softened butter, add it to the bowl, and whisk again until it’s all incorporated and has the consistency of mayonnaise.
Spoon half of the buttercream into the prepared cake ring. Spread all the chopped strawberries on top and press them into the cream.
Reserve 2 tablespoons buttercream in a small bowl and add the rest on top of the strawberries, smoothing the surface evenly. The filling should reach the tops of the strawberry slices inside the cake ring.
Place the second slice of cake on top of the cream, cut side up, fitting the layer inside the ring of strawberries but not covering the decorative ones on the outside, and soak it with the remaining orange syrup.
Spread the reserved 2 tablespoons buttercream on top of the cake. Refrigerate for about 4 hours or overnight.
Before serving, whip the cream in the chilled bowl of a stand mixer fitted with the whisk attachment, adding the sugar little by little until firm. Spoon it on top of the cake and flatten it out to the edges of the cake ring.
Remove the parchment paper by pulling the pieces out from under the cake.
Hold a warm, damp towel around the cake ring for a few seconds. This will allow the cake ring to separate from the cake more easily. Remove the ring and voilà! You have a beautiful birthday cake!
For the Sticky Caramel Sauce: Place the sugar in a heavy medium saucepan. Add the water gradually—you want to add just enough to bring the sugar to the consistency of wet sand.
Cook over low heat until the sugar dissolves, swirling the pan occasionally but not stirring. Increase the heat to medium and boil, still without stirring, until the sugar caramelizes and turns a deep brown, 7 to 10 minutes.
Remove the hot pan from the heat, place a strainer over the saucepan, and gradually and carefully pour in the cream. (The strainer prevents dangerous splattering from the hot caramel.)
Carefully stir in the cream, return the pan to low heat, and simmer the sauce, stirring occasionally, until it is smooth and thick, about 3 minutes. Cool, cover and refrigerate.
To serve, warm it over medium heat until melted and thin it with additional cream or milk if needed.