Making the Pastry Circles:

1. Combine Dry Ingredients and Butter: Begin by placing the all-purpose flour, salt, and cold, cubed unsalted butter into the bowl of a food processor. Pulse in short bursts until the mixture resembles coarse crumbs. The butter should still be in small pieces, about the size of peas. This step is critical for creating flaky layers, so avoid over-processing. If you don’t have a food processor, you can use a pastry blender or your fingertips to cut the butter into the flour, working quickly to keep the butter cold.
2. Prepare the Wet Ingredients: In a separate medium-sized bowl, whisk together the large eggs, ice water, apple cider vinegar, and vanilla paste until well combined. The ice water is essential for keeping the butter cold and preventing the gluten from developing too much, which can lead to a tough pastry. Apple cider vinegar also contributes to tenderness.
3. Combine Wet and Dry Ingredients: Gradually pour the egg mixture into the food processor with the flour-butter crumbs while pulsing intermittently. Continue pulsing until the dough just starts to come together and form a ball. Be extremely careful not to overmix at this stage. Overmixing will develop the gluten in the flour, resulting in a tough pastry rather than a flaky one. You want the dough to be just combined, with some streaks of butter still visible – this is perfectly fine and contributes to the flakiness.
4. Divide and Chill the Dough: Turn the dough out onto a lightly floured surface. Divide the dough into 8 equal portions. You can use a kitchen scale to ensure they are precisely the same size for even baking. Roll each portion into a ball and then flatten it slightly into a disk. Wrap each dough disk tightly with plastic wrap, ensuring no air is trapped inside. Refrigerate the wrapped dough disks for at least 2-3 hours, or ideally overnight. This chilling time is crucial. It allows the gluten to relax, making the dough easier to roll out, and it also allows the butter to firm up again, which is essential for creating distinct flaky layers during baking. You can even prepare the dough several days in advance and store it in the refrigerator, making this cake preparation more manageable over time.
5. Preheat Oven and Prepare Baking Sheets: When you’re ready to bake, preheat your oven to 375°F (190°C). Line several baking sheets with parchment paper. Parchment paper is essential to prevent the delicate pastry circles from sticking to the baking sheets.
6. Roll Out the Pastry Circles: Take one dough disk out of the refrigerator at a time (keep the rest chilled). Place it on a piece of parchment paper. Lightly dust the dough and your rolling pin with flour. Roll out the dough into a very thin circle, aiming for about 1/8 inch thickness. The thinner you roll the dough, the flakier your pastry layers will be. Use a round mold, a plate, or a pan that’s approximately 8 inches in diameter as a guide. Place the mold or plate on top of the rolled-out dough and use a sharp knife or pizza cutter to trim around the perimeter, creating a uniform circle. Repeat this process for all eight dough portions. Don’t discard the trimmings! We’ll bake these as well and use them for the crumb coating later.
7. Prick the Pastry Circles: Before baking, use a fork to prick the pastry circles all over. This step is vital to prevent the dough from puffing up excessively during baking and ensures that they bake flat and evenly.
8. Bake the Pastry Circles: Carefully transfer the parchment paper with the pastry circle onto a prepared baking sheet. Bake for about 10-12 minutes, or until the pastry is golden brown and crisp. Keep a very close eye on them, as they can burn quickly, especially at the edges. Baking time can vary slightly depending on your oven, so start checking for doneness around 10 minutes. You can bake multiple pastry circles at once if your oven is large enough and heats evenly, but if you notice uneven baking, it’s best to bake them in batches to ensure consistent results.
9. Cool and Separate Rings (if necessary): Remove the baked pastry circles from the oven and let them cool completely on the baking sheets. As they cool, they will become even crispier. If the baked pastry circles and the pastry rings (trimmings) that were baked alongside them have somewhat baked together, carefully run a thin, sharp knife between the circles and the rings to detach them while they are still slightly warm. Transfer the detached pastry rings (trimmings) to a ziplock bag and seal it tightly. Once completely cooled, crush the baked pastry rings into fine crumbs using a rolling pin or your hands. Set aside the pastry crumbs; these will be used to decorate the outside of the cake and add a delightful textural element.

Making the Egg Yolk Cream:

1. Whisk Egg Yolks and Sugar: In a medium-sized bowl, whisk together the egg yolks and granulated sugar until the mixture is pale yellow and slightly thickened. Adding a tablespoon or two of milk from the 4 cups (mentioned in the ingredients) can help to loosen the mixture and make it easier to whisk.
2. Incorporate Flour: Add the ⅔ cup of all-purpose flour to the egg yolk mixture. Whisk continuously until you have a completely uniform and lump-free batter. Again, if the batter seems too thick, you can add a little more milk (from the 4 cups) to help achieve a smooth consistency.
3. Heat the Milk: In a medium-sized saucepan, pour in the remaining whole milk (about 3 ¾ cups). Heat the milk over medium to medium-high heat until it just begins to simmer and tiny bubbles appear around the edges – do not let it boil vigorously. Stir the milk frequently with a whisk or spatula to prevent it from sticking to the bottom and scorching.
4. Temper the Eggs: This is a crucial step to prevent the egg yolks from scrambling when you add them to the hot milk. Slowly and gradually pour a small amount of the hot milk into the egg yolk mixture while whisking constantly and vigorously. This warms up the eggs and gently raises their temperature. Continue adding the hot milk in a slow, steady stream, whisking continuously until about half of the hot milk has been incorporated into the egg yolk mixture.
5. Cook the Cream: Pour the tempered egg yolk mixture back into the saucepan with the remaining hot milk. Place the saucepan back over medium heat and stir constantly with a whisk or spatula. Continue stirring without stopping until the mixture thickens significantly and comes to a gentle boil. This process should take about 5-7 minutes. You’ll know the cream is ready when it coats the back of a spoon and leaves a trail when you run your finger through it. It is important to stir constantly to prevent the cream from scorching at the bottom of the pan.
6. Incorporate Butter and Vanilla: Remove the saucepan from the heat immediately once the cream has thickened. Add the unsalted butter (cut into pieces for faster melting) and vanilla paste to the hot cream. Stir vigorously until the butter is completely melted and fully incorporated into the cream, resulting in a smooth and glossy custard.
7. Cool the Cream: Transfer the hot egg yolk cream to a clean bowl. To prevent a skin from forming on the surface as it cools, press a piece of plastic wrap directly onto the surface of the cream, ensuring it makes full contact. Let the cream cool completely at room temperature first, and then refrigerate it until it is thoroughly chilled and firm. This chilling process will further thicken the cream and make it easier to spread and layer in the cake.