"Dense, chewy sourdough English muffins full of wholesome goodness. To serve, pierce sides all the way around the round with a fork; pull apart. Toast in toaster or under the broiler. To store, refrigerate or freeze in a sealed container."
Combine 1 cup whole wheat flour, water, and sourdough starter in a large bowl. Stir thoroughly and cover with a clean towel. Let sit until spongy, 7 hours to 1 day.
Stir remaining 1/2 cup whole wheat flour, amaranth flour, honey, baking soda, and salt into the starter mixture. Mix in all-purpose flour, 1/2 cup at a time, until the dough is no longer sticky. Knead gently until dough is smooth and elastic.
Roll out dough on a floured work surface to 1/2-inch thickness. Cut into rounds with a 2 1/2-inch biscuit cutter. Sprinkle some cornmeal over a baking sheet. Transfer rounds to the baking sheet; sprinkle tops with remaining cornmeal. Cover with a clean towel and let rise until puffy, about 45 minutes.
Heat a large skillet over medium heat. Place rounds into hot skillet and lower heat to medium-low. Cook until golden brown and edges look dry, about 6 minutes per side. Transfer to a wire rack to cool completely.