To make the dough:

Heat the milk in the microwave for 30 seconds.

Add the yeast and dilute, then add 2 tablespoons of sugar and 1 cup (125g) of flour. Mix well.

In the mixer bowl, combine the remaining flour, sugar, and salt.

Add the eggs, vanilla, and yeast mixture.

Knead for 5 to 8 minutes, or until the dough is soft and elastic.

Transfer the dough to a lightly oiled bowl, cover with plastic wrap.

Let it rise at room temperature for 2 hours, then refrigerate overnight.

For the folding:

Roll out the dough on a floured surface into a large rectangle of 18″ x 13″ x 1/4″ (35 cm x 30.5 cm x 0.5 cm).

Spread the butter on 2/3 of the dough and fold in 3 (the unbuttered part in the middle, then the last 1/3 on top).

Refrigerate for 30 minutes.

Turn the dough 1/4 turn and roll out again.

Fold in 3 and refrigerate for another 30 minutes.

Repeat the operation 3 times.

Roll out the dough on a floured surface into a large rectangle of 36″ x 12″ x 1/4″ (70 cm x 30 cm x 0.5 cm).

Cut the dough into 8 equal rectangles.

Place one (or two) chocolate bars at the edge of each rectangle and roll up the dough all around, without tightening too much.

Place the chocolate-filled croissants on two baking sheets lined with silicone mats or parchment paper, making sure to position the folded side of the dough underneath the croissants.

Brush with the beaten egg mixed with a little milk and let rise at room temperature for about 2 hours.

Preheat the oven to 350 F (180 C).

Brush with the egg wash again and bake the croissants for 20 minutes, or until the tops are golden brown.

Let cool on a wire rack.