Step 1In a large pot, combine the brown sugar, vinegar, cider, cinnamon and butter. Bring to a boil, then reduce the mixture to a simmer, and cook, stirring occasionally, until reduced to 1 ½ cups, about 45 minutes. Discard the cinnamon. The syrup can be made up to 1 month in advance; cover tightly and refrigerate until needed, then warm and stir well before serving.
Step 1In a small bowl, combine the yeast and warm water. Set aside until foamy, about 10 minutes.
Step 2In a large bowl, whisk together the eggs and milk. In another large bowl, whisk together the cornmeal, flour, salt and sugar. Add the yeast mixture to the eggs and milk, then whisk in the flour mixture until thoroughly combined. Whisk in the melted butter until just combined. Cover the bowl with plastic wrap and refrigerate for at least 4 hours, up to overnight.
Step 3Heat the oven to 250 degrees. Heat the waffle iron and grease lightly with oil. Set a wire rack over a baking sheet.
Step 4Remove the batter from the refrigerator and whisk in the baking soda. Ladle some batter into the waffle iron, close the lid, and cook until the waffles are golden and cooked through, about 3 minutes or according to the manufacturer’s instructions. This makes about a dozen waffles, depending on the size of your waffle iron.
Step 5Transfer the waffle to the rack to keep warm in the oven. Repeat with the remaining batter, placing the cooked waffles in a single layer on the rack.
Step 6Serve the waffles warm with warm apple cider syrup.