Melt butter in a medium skillet over medium-high heat. Add grains and/or seeds and cook 5 to 7 minutes, stirring often until toasted (if the grains/seeds start to pop, you can cover the skillet). Remove from heat; cool completely.In a large bowl, stir together yeast, salt and warm water. Stir in flour and toasted grains with a wooden spoon until a dough forms and no dry parts remain. Cover bowl with lightly greased plastic wrap. Let rise in a warm place until doubled, about 2 to 3 hours.Punch down risen dough. Divide dough in half; reserve one half in a covered bowl in the fridge.* Lightly dust a surface with flour and shape dough on surface into a round loaf. Lightly sprinkle cornmeal on a pizza peel or the back of a baking sheet; transfer loaf to peel. Cover with lightly greased plastic wrap or a tea towel and let rise 40 minutes to 1 hour until puffy.When dough is halfway through its second rise, heat oven to 450 degrees F. Place a broiler pan on the bottom rack of the oven and a baking stone on the middle rack. Let the stone heat for 20 minutes.Dust top of loaf with flour. Using a serrated knife, lightly score top of bread three times. Slide bread from peel onto stone. Pour 1 cup hot water into the broiler pan and quickly close oven door.Bake bread 30 minutes until golden brown and tested for doneness.*The second loaf can be stored in a covered container in the fridge for up to 2 weeks. If you want to bake both loaves the same day, leave the second loaf out for a full hour (instead of 40 minutes to 1 hour) before you plan to bake it, then proceed as directed.