Direction for the sponge cake layer
 

• 30 minutes or longer before baking, set an oven rack in the center of the oven, preheat the oven to 165C°/ 325F°. 
   
• Lightly butter one 23 cm ( 9-inches) round layer-cake pan or use a springform.
   
• Pour in some flour in the cake pan/ springform pan and shake it around until the pan is evenly coated, invert, and tap lightly to shake out excess, and line the bottom with parchment paper and then set aside.
   
• In a medium bowl sift together the 100-gram all-purpose flour, and 1/2 teaspoon baking powder and set aside for now.
   

Make the yolk mixture.
 

• In the bowl of a stand mixer fitted with the whisk attachment, ( or in a large bowl and using an electric beater ) whip the 80 gram of egg yolks, 50-gram sugar, and 1 teaspoon vanilla bean paste, on medium speed, until light pale and yellow, about 3 to 5 minutes. Set aside for now, or if you have two mixers keep it moving at low speed until you are ready with the meringue mixture.
   

Make the meringue mixture.
 

• Wipe your mixer bowl and whisk with a paper towel dampened with a little lemon juice to eliminate any trace of grease.
   
• Put the 120-gram egg whites, and 1/4 teaspoon cream of tartar in the mixer bowl and whip on medium-high speed until bubbles start to form 2 to 3 minutes.
   
• With the mixer on low, slowly add the 110 gram of superfine sugar a tablespoon at a time and mix until the meringue is shiny and holds medium-stiff peaks, 5 to 7 minutes. Remove the bowl from the mixer.
   
• Pour over the egg yolk mixture and gently fold them together until fully combined, as little as possible!
   
• Sift the flour mixture onto the egg mixture in two increments. For maximum volume, use a balloon whisk or A large silicone and gently fold the flour mixture into the batter until fully incorporated.
   
• If using the whisk, periodically shake out the batter that collects inside, work quickly once the eggs are beaten so that they don’t deflate. Use a large silicone spatula at the end of folding in order to reach the bottom of the bowl and scrape the batter into the pan.
   
• Pour the cake batter into your prepared springform.
   
• Bake the cake in the center of the oven at 165C°/ 325F° until the cake layers are golden brown and spring back when gently touched with your fingertip and a toothpick inserted into the center of each cake comes out clean. about 18 to 20 minutes. 
   
• Avoid opening the oven door before the minimum baking time has elapsed because this fragile cake could fall. Test toward the end of baking by opening the oven door a crack, and if the cake doesn’t appear done, continue baking for some minutes more.
   
• Cool the cake on a wire rack, and cool completely.
   
• The cake layer is baked in a 23 cm / 9-inch springform, but it needs to be placed in a smaller springform or an adjustable cake ring so that there are no gaps between the cake and the springform or the pastry cream will run down the side while it bakes. I use an adjustable cake ring, A cake ring is basically a cake pan with no top or bottom.
   
• If you don't have an adjustable cake ring, use a 20 cm/8-inch springform, place the cooled cake in the springform, there should be no gap between the springform and sponge cake.
   
• If you are using an adjustable cake ring as I use ( see step by step photos in notes) cover a baking sheet with a baking mat or parchment paper and place the sponge cake on the baking sheet, use an adjustable cake ring, and adjust the cake ring to 20 cm/ 8-inches or until you see no gap between the cake and the ring. Set aside for now while you prepare the pastry cream.
   

Directions for the pastry cream 
 

• 30 minutes before you make the vanilla bean flan, Preheat the oven to 200C°/400F° use both the heat on the bottom and on the top. Be aware that once the oven is preheated and you are ready to bake the flan, you need to lower the oven temperature to 175C°/350F°, and you need to turn off the heating element on the bottom of the oven, ( not the top) 
   
• For the pastry cream, pour 450-gram heavy cream and 700-gram whole milk into a large saucepan.
   
• Use a sharp knife to split 2 vanilla beans lengthwise and scrape the seeds into the cream/milk put the pods in the mixture as well, give it a quick whisk so that the vanilla seeds are combined with the cream and milk. If you are using vanilla bean paste instead add 2 tablespoons of vanilla bean paste instead of the vanilla beans.
   
• Heat the cream/milk over medium heat until almost boiling ( bubbles will begin to form at the edges).
   
• Remove from heat, cover, and let steep for 1 hour if time permits for maximum vanilla flavor otherwise, proceed as directed.
   
• If you have steep the milk/cream vanilla mixture, reheat over medium heat until just to a simmer.
   
• Meanwhile, In a large bowl whisk together 225 gram superfine or white sugar, and 90-gram corn starch give it a quick whisk to combine these two.
   
• Add 4 large eggs, and 4 large eggs yolks, use a piano whisk and whisk together until light and smooth, do this while you heat ( re-heat) the milk/cream and not too far in advance!
   
• As you continue whisking, slowly add one-third of the hot cream/milk vanilla mixture into the egg/yolk mixture to temper the eggs/eggs yolks. 
   
• Gradually whisk in remaining milk/cream into the eggs/eggs yolks.
   
• Pour the content of the bowl back into the saucepan, Make sure to scrape all the flavorful gooey vanilla seeds into the saucepan that is at the bottom of the bowl.
   
• Return the saucepan to medium heat and bring the mixture to a boil. make sure to whisk continuously, whisk until the pastry cream thickens, and you see large bubbles on the surface,  depending on the heat and what saucepan you are using this can takes anywhere from 5 up to 25 minutes. 
   
• When the mixture slightly thickens and you see larges bubbles on the surface, continue to whisk for 1 to 2 minutes more to cook off the cornstarch otherwise the pastry cream will taste chalky in your mouth. 
   
• Remove from heat, if there are any lumps in the pastry cream strain it through a fine-mesh sieve, make sure you squeeze out all of the gooey vanilla seeds and add it back into the pastry cream, discard the vanilla bean.
   
• Make sure to scrape all the flavorful gooey vanilla seeds from the bottom of the saucepan back into the pastry cream.
   
• Give the pastry cream a quick whisk and immediately pour the warm pastry cream, on top of the cooled sponge cake into the prepared springform or adjustable cake ring.
   
• Turn the oven temperature down to 175C°/350F° turn off the heating element on the bottom of the oven, ( not the top), and bake the flan immediately for 60 minutes or until the top has a beautiful brown color.
   
• This flan cake as seen in my step-by-step photos will shrink just a little bit and might have some cracks on the side of the pan so don't be alarmed, this is perfectly normal.
   
• Cool the flan at room temperature, then cover tightly with plastic wrap or aluminum foil and refrigerate for at least 6 to 8 hours and up to 3 days. For best result overnight is best.
   
• Just before serving, use a knife to loosen the chilled flan from the rim of the adjustable cake ring or springform, then remove the cake ring.
   
• Using a clean sharp knife, cut into slices for serving, for neat slices, wipe the knife clean between each slice.
   
• Cover and store leftover flan in the refrigerator for up to 3 days.