Combine 1/4 cup warm water, yeast, and 1 tsp sugar. Let sit 5-10 minutes until foamy. In a large bowl, whisk flour, remaining sugar, and salt. Add discard, yeast mixture, remaining water, and butter. Stir until a shaggy dough forms.

Knead by hand for 8-10 minutes on a floured surface, or in a stand mixer with a dough hook for 6 minutes, until smooth and elastic.

Place in a greased bowl, cover, and let rise in a warm spot until doubled, about 1 to 1 1/2 hours.

Grease a 9x5-inch loaf pan. Punch down dough, pat into an 8x10-inch rectangle, roll tightly, pinch seam, and place seam-side down in pan. Cover and proof until dough rises just above the rim, 45 minutes to 1 hour.

Preheat oven to 350°F (180°C) toward the end of proofing. Bake for 30-35 minutes until deep golden and internal temp reaches 190-200°F (88-93°C).

Cool in pan 5 minutes, then turn out onto a rack and cool completely before slicing.