In a large bowl, whisk flour, cornmeal, sugar, baking powder, and salt. In a medium bowl, whisk egg, buttermilk, and 1 Tbsp. oil. Add egg mixture to dry ingredients and stir until a thick batter forms. Let sit until hydrated, about 5 minutes.

Meanwhile, into a large, heavy pot, pour oil to a depth of 2 inches. Heat over medium-high heat until a deep-fry thermometer registers 350°F.

Pour batter into a tall glass, if desired. Insert a skewer through sausage and dip into batter, coating completely. Holding skewer, carefully lower sausage into oil.

Fry, turning occasionally, until golden brown, about 2 to 3 minutes. Transfer to a wire rack set in a baking sheet to drain.

Arrange mini corn dogs on a platter. Serve warm with mustard and/or ketchup alongside.