Reserve 1/4 cup of the milk in a bowl and heat the remaining milk in a small saucepan—do not let it boil.

To the bowl with the cold milk, add the egg yolks, vanilla, cornstarch, and sugar. Whisk thoroughly until smooth.

Once the milk is hot, slowly pour half of it into the egg mixture, whisking constantly.

Return the mixture to the saucepan with the remaining milk and cook over medium heat, stirring continuously until thickened.

Once bubbles appear on the surface, remove from heat and stir in the butter until fully melted.

Transfer the cream to a shallow dish and cover with plastic wrap, pressing it directly onto the surface to prevent a skin from forming.

Let it cool, then refrigerate until completely chilled.

In a stand mixer bowl, combine the lukewarm milk, yogurt, sugar, and yeast. Stir until the sugar dissolves.

Add the flour and mix on low speed for 2-3 minutes, until the flour is hydrated.

Increase speed and knead for 4-5 minutes.

Add the salt and gradually incorporate the soft butter while mixing.

Continue kneading for 8-10 minutes until you have a soft, smooth, and elastic dough.

Cover and let it rest in a warm place for at least 1½ hours, until doubled in size.

Lightly grease your hands with butter or oil and transfer the dough to a lightly floured surface.

Gently deflate and roll it out into a large rectangle (40 x 60 cm).

Remove excess flour and spread the chilled cream evenly over the surface.

Sprinkle the chocolate chips on top.

Fold the dough into thirds, like a letter. Using a sharp knife, cut into strips about 3 cm wide.

Twist each strip several times, then coil it into a spiral shape. Pinch the bottom to seal.

Place the rolls on a baking sheet lined with parchment paper, leaving space between them.

Cover and let them rise in a warm place for about 40 minutes.

Brush with the egg wash. Bake in a preheated oven at 200°C (fan/convection setting), on the middle rack, for about 15 minutes, until evenly golden.