Activate the Yeast: In a small bowl, combine the warm milk, water, and sugar. Sprinkle the yeast over the top and let it sit for 5–10 minutes until it becomes bubbly.
Prepare the Dough: In a large bowl, mix the flour and salt. Add the yeast mixture and oil, and knead until the dough is smooth and elastic. If the dough is too sticky, add a bit more flour as needed.
Let the Dough Rise: Cover the dough with a clean kitchen towel and place it in a warm spot to rise for about 1 hour, or until it doubles in size.
Shape the Buns: After the dough has risen, punch it down and roll it out into a flat sheet. Cut the dough into small squares, approximately 2–3 inches in size. Place a small amount of chocolate spread in the center of each square.
Form the Buns: Fold the dough squares over the filling to create a sealed bun. Pinch the edges to ensure the chocolate is securely enclosed inside.
Prepare for Baking: Place the formed buns on a baking tray lined with parchment paper. Beat the egg yolk with 1 tablespoon of milk and brush this mixture over the tops of the buns. Optionally, sprinkle poppy seeds on top for extra crunch.
Bake the Buns: Preheat the oven to 180°C (350°F). Bake the buns for 20–25 minutes, or until they are golden brown and cooked through.
Cool and Serve: Let the buns cool on a wire rack for a few minutes before serving. Enjoy warm or at room temperature.