Warm the water with a microwave etc. Add instant coffee to the warmed water and melt it well. Cool it to 40℃ / 104 F or less. Crush the lumps of dry milk and make it powder-like.

Put bread flour and dry milk in a large bowl, and stir well. Make a dent and put sugar and dry yeast into it. Add salt to the edge away from the dry yeast.

Pour the coffee water over the sugar and dry yeast, and then pour over the flour while drawing circles. Roughly mix with a spatula until the dough almost comes together.

Put the dough in a stand mixer. (I used KitchenAid Artisan 3.3L.) Knead it for 2-3 minutes at speed 2. Then knead for 10 minutes at speed 4. In the middle of kneading, remove the dough from the hook, and turn it over. (Knead for 5 minutes, turn over and knead again for 5 minutes.)

Add the softened butter. Knead for 10-12 minutes at speed 4 until smooth. In the middle of kneading, remove the dough from the hook, and turn it over. (Knead for 5-6 minutes, turn over and knead again for 5-6 minutes.) If the dough doesn't hold together, try to turn up the speed for a short time.

Put onto a work surface. Use your hand to hit the dough against the work surface. Fold in half. Repeat it 50 times. Use your hands to stretch gently one part of the dough thinly. It's ready if it doesn't tear.

Shape it into a ball and put it in a lightly oiled bowl. Cover it with cling wrap and let it rise at 35℃ / 95 F (or a warm place) for 60-90 minutes until 1.5-2 times in size. Finger Dent Test! Press your floured finger into the dough. It's ready if the dent springs back a little and it stays without filling in.

Press it gently to remove the air. Divide it in half. Punch down, and shape each into a ball. Cover with a tightly wrung wet cloth and leave for 15 minutes.

Punch down one to flatten. Turn it over to put with the smooth side facing down. Flour the dough and your rolling pin. Roll it out into a rectangle, about 20cm × 18cm, 7.8'' × 7''. Punch down the other to flatten, and turn over, roll out into a little bit smaller rectangle.

Sprinkle half of the chocolate chips over the large rectangle and lightly press them into the dough. Place the smaller rectangle on the top and sprinkle the rest of the chocolate chips over it, and lightly press them into the dough.

Roll up gently from the back toward the front while being careful not to let air in as much as possible, not too tight, not too loose. Pinch the seams to stick together.

Place it in a lightly oiled loaf pan with the seam side facing down. Let it rise at 40℃ / 104 F (or a warm place) for 60-90 minutes until the top of the dough is higher a little than the height of the pan. Preheat the oven to 210℃ / 410 F. Gently brush them with egg wash.

Turn down the oven to 200℃ / 392 °F and bake it for 30 minutes until dark brown. Drop the pan to prevent shrinkage. Remove the bread from the pan and cool it down on a rack.