Cut 1 stick of butter (8 tablespoons) into 12 slices and arrange them in a 4x3 grid on one side of a large piece of parchment paper. Fold the parchment paper over the butter and fold the open edges so that the parchment paper is approximately 6x6 inch square. Use a rolling pin the roll the butter into one flat 6x6 inch piece. Refrigerate the parchment paper wrapped butter, rolling pin, and pastry molds until needed.

In a medium size mixing bowl, use a pastry cutter (or two knives) to cut the remaining 2 tablespoons of butter in 1 ½ cup flour, 1 teaspoon sugar, and salt until the butter looks like grains of sand. Add the ice water and mix with a wooden spoon until a dough forms. If the dough seems too shaggy, add 1 tablespoon of flour. If a dough doesn't form, add 1-2 teaspoons of ice water, one teaspoon at a time. Lightly flour a large cutting board and knead the dough a few times until the dough is smooth. Shape the dough into a square, wrap the dough with plastic wrap, and refrigerate for 20 minutes to let the dough rest.

Lightly flour the rolling pin and cutting board, use a rolling pin to roll the dough out into an approximately 9x9 inch square. Unwrap the butter square and place it diagonally on top of the dough and fold the corners down to wrap the butter, gently stretching the edges if needed. Pinch the edges close with your fingers and use a lightly floured rolling pin to the roll the dough edges together. Wrap with parchment paper and refrigerate the dough and the rolling pin for 20-30 minutes.

Lightly flour the rolling pin and cutting board, unwrap the dough and roll it into a rectangle and fold the left third toward the center and the right third toward the center (like a letter). Wrap the dough with parchment paper and refrigerate along with the rolling pin for 20-30 minutes.

Lightly flour the rolling pin and cutting board, unwrap the dough and roll it into a long rectangle (18x4 inches) and fold the two ends to the center and fold in half into a square. Wrap with parchment paper and refrigerate for 20-30 minutes.

Lightly flour the rolling pin and cutting, unwrap the dough. Use your rolling pin to press down several times on the pastry square to flatten the dough, then roll it out into a large square (approximately 12x12 inch). Brush off any excess flour, and use your fingers to roll the square into a tight log, wrap with parchment paper, and refrigerate for 20-30 minutes or until ready to assemble.

You will need 15 minutes of uninterrupted work time to make the custard filling, ideally during one of the breaks while waiting for the puff pastry to rest. In a small 1-quart saucepan, beat the egg yolks with a whisk. Add milk, heavy whipping cream, sugar, and cornstarch, stir to combine. Cook the egg mixture on low-medium heat, stir constantly until you see a whisp of steam, and the egg mixture thickens slightly (approximately 8-10 minutes). Test by dipping a clean spoon into the custard and then run your finger across the back of the spoon and if there’s a clear line, remove from heat immediately.

Add the vanilla and stir to combine. Pour the filling through a fine mesh strainer into 2 cup spouted measuring cup or a bowl, discard any solids. Allow the custard to cool to room temperature, cover, and then refrigerate until ready to fill the pastry cups.

When ready to assemble the custard filling with the puff pastry, check that the oven rack is in the middle and preheat the oven to 425°F. Take the egg tart molds out of the refrigerator.

Unwrap the log, trim off the rough edges, and set aside the scraps. Cut the log in half, cut each half into quarters, and cut each quarter into 3 pieces. Keep the cut pieces of dough covered with parchment paper as you shape the dough into the pastry molds.

Place a piece of dough into an egg tart mold cut side down and use your thumb to press the center of the dough spiral onto the base of the mold. Use your thumbs to press the dough onto the side of the mold while gently pulling the dough up toward the top edge so that there’s a little rim of dough above the edge of the mold. Repeat until all the molds are shaped and if it’s a hot day, refrigerate them for 10-20 minutes.

Work at a kitchen counter closest to your oven, place the pastry molds onto a rimmed baking sheet and neatly fill the pastry shells with approximately 2 tablespoons of filling (85% full). I use a soup ladle with a pouring spout.

Place the tray of filled pastry shells into the oven and bake for 25 minutes. Set a timer for 20 minutes to check on their progress. They are ready when pot tat shells are golden brown, the filling is bubbly, and the tops have a slightly caramelized appearance. Allow to cool for at least 10-15 minutes and serve warm or at room temperature.