Preparing the Laminated Dough:

1. Combine flour and salt in a stand mixer bowl. Gradually add cold water, mixing on low speed until a soft dough forms.
2. Shape the dough into a square on a floured surface. Cover and rest for 15 minutes.
3. Roll the dough into an 18-inch square, keeping thickness even and edges straight.
4. Dot two-thirds of the dough with butter, spread evenly, leaving a clean border.
5. Fold the unbuttered third over the center, then fold the opposite end over that. Rotate 90 degrees.
6. Repeat the rolling and folding process two more times, chilling dough between folds if it softens.
7. For the final turn, roll into a rectangle and tightly spiral the dough into a log. Chill.

Crafting the Custard:

1. Create a paste by mixing 30g flour with a small portion of milk until smooth.
2. In a saucepan, heat sugar and water to 220°F (100°C) to make a syrup.
3. Heat the remaining milk until just below boiling. Gradually mix the hot milk into the flour paste.
4. Slowly stream in the sugar syrup while whisking. Add vanilla bean seeds.
5. Whisk in egg yolks carefully and strain the mixture to remove lumps.

Assembly and Baking:

1. Preheat the oven to 550°F (290°C) with baking stones in place for at least an hour.
2. Slice the chilled dough log into portions and place cut-side down in muffin tins.
3. Using moistened thumbs, press dough into thin shells with slightly raised edges.
4. Fill each shell three-quarters full with custard mixture.
5. Bake for 10-12 minutes, monitoring for caramelization on top.