Heat water to 120 degrees F (49 degrees C) to 130 degrees F (54 degrees C) in a saucepan. Transfer to a glass bowl; add yeast. Cover with plastic wrap; let stand about 10 minutes.
Stir melted butter and sugar together in a bowl. Add butter mixture to yeast water; stir in starter.
Combine 3 cups flour and salt in a large bowl. Add starter mixture slowly; mix well. Stir in 2 cups flour; turn dough out onto a lightly floured surface.
Knead in as much remaining flour as possible to create a stiff, smooth ball, at least 10 minutes. Transfer ball to a lightly oiled bowl; cover with plastic wrap. Let rise until doubled, 45 minutes to 2 hours.
Punch dough down; turn out onto a floured surface. Divide into 14 balls; cover and let rise for 30 minutes.
Preheat oven to 375 degrees F (190 degrees C). Sprinkle cornmeal onto a baking sheet; place dough balls on top.
Place baking sheet into the preheated oven. Spray the walls of the oven with water once to create steam; bake until tops are golden, for a total of 20 to 25 minutes. Cool on a wire rack.