In a small bowl, combine warm milk and active dry yeast, allowing it to sit until frothy, about 5–10 minutes.

In a large mixing bowl, mix the sugar, eggs, and vanilla extract, followed by the yeast mixture.

Gradually add all-purpose flour and salt, then fold in softened butter.

Knead the dough for 8–10 minutes by hand or 5–6 minutes with a stand mixer until it’s smooth and slightly sticky.

Transfer the dough to a greased bowl, covering it with a clean kitchen towel. Allow it to rise in a warm location until doubled in size, about 1 hour.

In a saucepan, heat whole milk until hot but not boiling.

In a separate bowl, whisk together egg yolks, sugar, cornstarch, and a pinch of salt.

Gradually pour the warm milk into the egg mixture, whisking continuously, then return to the saucepan.

Cook over medium heat until thickened, stirring constantly. Remove from heat and stir in vanilla extract.

Roll the risen dough out onto a lightly floured surface into a rectangle.

Spread the cooled custard filling over the dough, leaving a small border. Sprinkle with chocolate chips.

Roll into a log shape, and slice into equal pieces, placing cut-side up in a greased baking pan.

Cover with a kitchen towel and let rise again until puffy, roughly 45 minutes.

Preheat your oven to 350°F (175°C). Brush tops with beaten egg and bake for 20–25 minutes until golden brown.

Remove from oven and let cool slightly in the pan. Dust with powdered sugar if desired, then serve warm.