In the bowl of a stand mixer, whisk together the warm milk, sugar, and active dry yeast. Let it sit for 5 to 10 minutes until foamy.

Add the egg, melted butter, and salt to the yeast mixture. Fit the mixer with the dough hook and add the all-purpose flour. Mix on low speed until incorporated, then increase to medium speed and knead for 8 to 10 minutes until smooth and elastic.

Transfer the dough to a lightly oiled bowl, cover with plastic wrap, and let rise for 1 to 1.5 hours until doubled in size.

Gently punch down the dough, reshape it into a ball, cover, and refrigerate for at least 1 hour.

While the dough chills, pound and roll the cold butter into an 8 by 8 inch square and refrigerate until firm.

Roll chilled dough into a 16 by 8 inch rectangle, place the butter block on one half, fold the other half over, and pinch to seal.

Roll the dough into a 24 inch long rectangle, fold one-third to the center, then the other third over it, and refrigerate for 30 minutes.

Repeat the rolling and folding process once more and chill for another 30 minutes.

Roll the dough into a final 12 by 18 inch rectangle, sprinkle with mini chocolate chips, and roll up tightly from the long side.

Cut into 12 pieces and place cut-side up in a greased muffin tin.

Cover with plastic wrap and let rise for 45 to 60 minutes until puffy.

Preheat oven to 400 degrees F (200 degrees C) and bake for 15 to 20 minutes until golden brown.

Cool in the pan for 5 minutes, then transfer to a wire rack and dust with powdered sugar.