Scratch Cornbread

1 cup white cornmeal
1 cup yellow cornmeal
1 cup all-purpose flour
2 teaspoons baking powder
1/2 teaspoon baking soda
2 teaspoons sugar (OR for sweet cornbread use 1 1/2 tablespoons Sugar)
2 teaspoons seasoning salt (OR for sweet cornbread use 1/2 teaspoon Kosher Salt)
1 large egg
2 1/2 cups buttermilk
1 tablespoon sour cream (heaping)
2 teaspoons jalapeno juice (or white vinegar)
2 tablespoons vegetable shortening (heaping, when scooped out solid)

Preheat oven to 450°F.
In a large bowl, sift together all dry ingredients. In a medium bowl, beat the egg then add sour cream, vinegar & buttermilk and beat again until thoroughly mixed.
Pour the egg/buttermilk/sour cream mixture into the dry ingredients and stir the mixture until smooth.
Melt shortening in a 10-inch cast-iron skillet on the stovetop using high heat, making sure to thoroughly coat the sides of the skillet with the shortening as the shortening melts (I stick a knife in one of the solid chunks of shortening and coat the sides of the pan until the shortening melts away).
Add melted shortening to the cornbread mixture, stir mixture thoroughly, and then pour mixture into the cast-iron skillet.
Keep skillet on high heat and let the mixture sit for about 30 seconds.
Remove skillet from stovetop and place in 450°F oven and bake for 20-25 minutes or until a light, golden brown.
Remove from the oven and let stand for 5 minutes then cut into wedges, serve hot and enjoy.