In a large Dutch oven or heavy-bottomed pot, begin heating your frying oil to 350°F (175°C). Use a deep-fry thermometer to monitor the temperature.

In a large mixing bowl, whisk together the yellow cornmeal, all-purpose flour, granulated sugar, baking powder, baking soda, and fine sea salt.

In a separate medium bowl, whisk the sourdough discard, buttermilk, egg, and melted butter until smooth and well combined.

Pour the wet ingredients into the dry ingredients and stir gently until just combined. Let the batter rest for 10 minutes. It should be very thick!

While the batter rests, insert a wooden skewer into each hot dog, leaving enough room at the bottom for a handle.

Thoroughly pat each hot dog completely dry with paper towels. Roll each dried hot dog lightly in the extra all-purpose flour, shaking off the excess. This is crucial to make the batter stick!

Transfer the rested batter into a tall, heavy drinking glass or a mason jar.

Holding the skewer, dip one hot dog straight down into the glass of batter, twirling it slightly as you pull it straight up to ensure an even, thick coating.

Immediately and carefully drop the battered corn dog into the 350°F oil. Fry 2 to 3 corn dogs at a time for 3 to 4 minutes, turning them occasionally with tongs until they are deep golden brown on all sides.

Transfer the fried corn dogs to a wire rack set over paper towels to drain. Serve immediately with your favorite mustards!