1. Combine Wet Ingredients and Starter: In a large mixing bowl, gently whisk together the active sourdough starter, warm water, and maple syrup until well combined. The mixture should look milky and slightly frothy.

2. Add Dry Ingredients: Stir in the salt and then gradually add the bread flour, one cup at a time, mixing with a wooden spoon or your hands until a shaggy dough forms. It should be sticky but come together into a mass. Cover the bowl with a damp kitchen towel or plastic wrap and let it rest for 30 minutes. This resting period, called autolyse, helps the flour fully hydrate.

3. Incorporate Butter and Begin Bulk Fermentation: After the rest, pour the melted butter over the dough. Gently knead the butter into the dough for a few minutes until it’s fully incorporated. The dough will feel a bit slippery at first but will eventually absorb the butter. Now, begin the bulk fermentation. Over the next 4-6 hours (or 8-12 hours if cold proofing in the fridge), perform a series of “stretch and folds.” Every 30-60 minutes during the first 2-3 hours, gently pull a section of the dough up from the edge of the bowl, stretch it, and fold it over the center. Rotate the bowl and repeat this 4-6 times for each set. This builds strength in the dough.

4. Shape the Loaf: Once the dough has visibly increased in volume (it should be bubbly and jiggling), gently turn it out onto a lightly floured surface. Shape it into a round or oval loaf, creating tension on the surface. You can do this by gently pulling the edges of the dough towards the center and then flipping it over to create a smooth top.

5. Final Proofing: Transfer the shaped dough into a floured banneton basket or a bowl lined with a floured kitchen towel, seam-side up. Cover it and let it proof at room temperature for 2-4 hours, or in the refrigerator overnight for 8-12 hours. The dough should feel puffy and slightly spring back when gently poked.

6. Preheat Oven and Score: About 30 minutes before baking, preheat your oven to 450 F (232 C) with a Dutch oven inside. Carefully remove the hot Dutch oven. Gently invert the proofed dough into the hot Dutch oven. If using an egg wash (for a golden crust), whisk the beaten egg with milk and brush it over the top of the dough. Using a sharp razor blade or knife, score the top of the loaf with your desired design.

7. Bake the Bread: Place the lid on the Dutch oven and bake for 30 minutes. Remove the lid and continue baking for another 10-15 minutes, or until the crust is deeply golden brown and the internal temperature reaches 200-210 F (93-99 C).

8. Cool Completely: Carefully remove the bread from the Dutch oven and transfer it to a wire rack to cool completely before slicing. This is crucial for the crumb to set properly and for the best texture and flavor.