In a large mixing bowl, combine the active sourdough starter and lukewarm water. Stir until the starter is dissolved in the water.
Mix Dough:
Add the bread flour, sugar or honey, melted butter, and salt to the bowl with the sourdough starter mixture. Stir until a shaggy dough forms.
Knead Dough:
Turn the dough out onto a lightly floured surface and knead for about 10-15 minutes, or until the dough becomes smooth and elastic.
First Fermentation:
Place the dough in a greased bowl, cover it with a damp cloth or plastic wrap, and let it ferment at room temperature for 12-24 hours, or until it has doubled in size and bubbles appear on the surface.
Shape Loaf:
After the first fermentation, gently deflate the dough and shape it into a loaf. Place the loaf in a greased loaf pan.
Second Proofing:
Cover the loaf with a damp cloth or plastic wrap and let it proof at room temperature for 2-3 hours, or until it has increased in size by about 50% and holds an indentation when gently pressed with a finger.
Preheat Oven:
About 30 minutes before baking, preheat your oven to 375°F (190°C).
Bake Bread:
Once the dough has finished proofing, remove the cover and transfer the loaf to the preheated oven. Bake for 35-40 minutes, or until the bread is golden brown and sounds hollow when tapped on the bottom.
Cool and Slice:
Remove the loaf from the oven and let it cool in the pan for 5 minutes. Then, transfer the loaf to a wire rack to cool completely before slicing.
Serve:
Once cooled, slice the sourdough sandwich bread and enjoy it fresh with your favorite sandwich fillings or spreads.
Note: Adjust the fermentation and proofing times based on your sourdough starter’s activity and the ambient temperature in your kitchen.