Homemade Potato Bread

Name: Homemade Potato Bread
Prep time: 25 min
Total time: 25 min
Cuisine: World Cuisine
Ingredients: 1 1/4 lukewarm water (or reserved potato boiling water); 2 tbsp. plus 1 tsp. granulated sugar, divided; 1 (.25-oz.) packet active dry yeast; 5 c. all-purpose flour; 1 c. boiled, mashed potato (from about 1 large russet potato); 2 tsp. kosher salt; 6 tbsp. butter, softened, plus more for pans; Cooking spray or extra-virgin olive oil; 2 tbsp. melted butter; Flaky sea salt (optional)