Ingredients

• 2.5 cups all-purpose flour , or more as needed, divided
• 1 cup water
• 0.33 cups sourdough starter
• 3 tablespoons unsalted butter , melted
• 1 tablespoon white sugar
• 0.75 teaspoons sea salt
• 1 teaspoon oil , or as needed, for oiling bowl
• 1 teaspoon unsalted butter , or as needed, for greasing pan
• 1 egg , beaten

Instructions

1. 1 Combine 2 cups flour, water, sourdough starter, 3 tablespoons butter, sugar, and salt in a bowl; mix into a stiff dough. Beat for a few minutes using a wooden spoon or an electric mixer; the dough should be quite moist and sticky.
2. 2 Place dough in a large, oiled bowl and turn to coat all sides. Cover the bowl with a clean towel. Leave to ferment at room temperature 8 hours to overnight.
3. 3 Turn dough out onto a liberally floured surface; knead at least 10 minutes, adding remaining 1/2 cup flour or more as needed. The dough should be very smooth and elastic when done.
4. 4 Grease a loaf pan with 1 teaspoon butter. Shape dough into a loaf and place in the prepared pan. Cover with a clean towel and let rise in a warm place until doubled in volume, 4 to 12 hours depending on temperature.
5. 5 Preheat the oven to 350 degrees F (175 degrees C).
6. 6 Brush top of loaf with beaten egg. Cut a 1/4-inch slash, lengthwise, down center using a sharp knife.
7. 7 Bake in the preheated oven until an instant-read thermometer inserted into center reads at least 180 degrees F (82 degrees C), 25 to 30 minutes.
8. 8 Turn loaf out onto a wire rack; cool completely before slicing.

Nutrition per serving