In a mixing bowl, combine your active sourdough starter, lukewarm milk, egg, granulated sugar, salt, and instant yeast. Mix it all together until combined, then gradually add the flour and 10 tablespoons of softened butter. Knead the mixture until it forms a smooth, elastic dough, which should take about 6-8 minutes with a mixer or 10 minutes by hand.

Cover the dough with a clean kitchen towel or plastic wrap and let it rest at room temperature for about 3-4 hours. You want it to be visibly puffed and slightly risen during this time.

While your dough is resting, prepare the butter for laminating. Place the 8 tablespoons of cold unsalted butter between two sheets of parchment paper. Use a rolling pin to pound it into a 7×7 inch square. Once shaped, chill this butter block in the refrigerator until it’s firm but still pliable.

Once the dough has risen, lightly flour your work surface and roll the dough into a 10×10 inch square. Take your butter block and place it diagonally in the center of the dough square. Fold each corner of the dough over the butter, completely enclosing it.

Now, roll the dough-butter package into a 10×20 inch rectangle. After rolling, fold the dough into thirds like a letter — this is your first turn. Wrap it up and chill in the fridge for about 30 minutes. After chilling, repeat the rolling and folding process two more times; each time, make sure to chill between turns for about 30 minutes.

After the final chill, roll the dough into a large rectangle, approximately 12×20 inches. Evenly sprinkle the chocolate chips over the surface. Fold or roll the dough to encase the chips, then shape it into a loaf form and place it into a greased loaf pan.

Cover the loaf pan with a towel and let the dough proof at room temperature for about 2 hours, or until it’s puffy and nearly doubled in size.

While the dough is proofing, preheat your oven to 375°F (190°C). Once ready, pop the bread into the oven and bake for about 30-35 minutes, or until it’s beautifully golden brown. If the top browns too quickly, simply tent it with some aluminum foil.

After baking, remove the bread from the oven and allow it to cool in the pan for around 10 minutes. Then transfer it to a wire rack and cool for at least 1 hour before slicing. You can enjoy it plain or toasted with a bit of butter — delicious!