PREP: Preheat the oven to 375 degrees F. Place eight tablespoons of butter in a microwave-safe bowl and melt. Set melted butter aside to cool to room temperature before using. Remove the wet ingredients from the refrigerator so they reach room temperature.
WET INGREDIENTS: In a large bowl, combine the buttermilk, egg, two tablespoons of honey, brown sugar, and white sugar. While whisking constantly, slowly drizzle in the melted (but room temperature) butter until smooth and combined. If the wet ingredients are cold and butter is warm, it will clump. Pour the wet ingredients into the center of the dry ingredients and gently mix (or fold with a spatula) until just combined. Do not over mix or beat.
DRY INGREDIENTS: In another large bowl, combine the flour, cornmeal, baking powder, baking soda, salt, and cornstarch.
PAN: Place the 1 tablespoon remaining butter in the 9x9-inch pan. Place in the preheated oven for exactly one minute and then remove using oven mitts. Tilt the pan to coat the entire bottom in the melted butter. Pour the prepared batter into this pan and use a spatula to spread and make the top even.
BAKE: Bake for 19-20 minutes or until the edges are golden brown and the center springs back when pressed gently.
FINISH: Place the pan on a wire cooling rack and let it cool for 10 minutes. Gently brush the remaining honey over the cornbread. Cut into squares and serve warm.
STORAGE: Cornbread does not keep well. It is best used on the day it's baked. To store leftovers, wrap individual pieces in plastic, then foil, and place in the fridge. If you are making cornbread for stuffing, it can be baked up to three days ahead (then store in an airtight container in the fridge).