Prepare the Dough:

1. Mix the Dough: In a large mixing bowl, combine the flour, sugar, salt, and yeast. Add the warm milk and egg, then mix until a dough forms. Knead for 5-7 minutes until smooth. Cover and let it rest for 30 minutes.
2. Laminate the Dough: Roll out the dough into a rectangle. Place the cold butter slices evenly over two-thirds of the dough. Fold the unbuttered third over the center, then fold the remaining third on top (like folding a letter). Turn the dough 90 degrees and roll it out again. Repeat this folding process 3 more times, chilling the dough for 20 minutes between each fold.
3. Shape and Proof: Roll out the dough to ½-inch thickness and use a round cutter to cut out donut shapes. Use a smaller cutter to create the center hole. Place the cronuts on a baking sheet, cover, and let them proof for 45 minutes until puffy.

Make the Vanilla Bean Pastry Cream:

4. Heat the Milk: In a medium saucepan, heat the milk and vanilla bean seeds over medium heat until it begins to simmer.
5. Whisk the Yolks and Sugar: In a separate bowl, whisk the egg yolks, sugar, and cornstarch until smooth. Slowly pour the hot milk into the egg mixture while whisking continuously.
6. Cook the Pastry Cream: Return the mixture to the saucepan and cook over medium heat, stirring constantly, until thickened. Remove from heat and stir in the butter. Cover and chill.

Fry the Cronuts:

7. Heat the Oil: Heat 3 inches of oil in a heavy-bottomed pot to 350°F (175°C).
8. Fry the Cronuts: Fry the cronuts in batches for 2-3 minutes per side, or until golden brown. Drain on a wire rack lined with paper towels.

Assemble the Cronuts:

9. Fill with Pastry Cream: Use a piping bag fitted with a small round tip to fill each cronut with vanilla bean pastry cream.
10. Glaze and Garnish: Dip the top of each cronut into the strawberry glaze. Garnish with fresh strawberry slices and a dusting of powdered sugar, if desired.