In a large bowl, place the flour, xanthan gum, cornmeal, sugar, baking powder and salt, and whisk to combine well.
Add the shortening and, with the tines of a fork or a pastry cutter, cut the shortening into the dry ingredients until the mixture resembles coarse sand. There will be some clumps.
To make 9 muffins, this dry mix weighs 495 grams total.
Store the dry mix in a sealed container in a cool, dry place until ready to use. For longer storage, place in the refrigerator or freezer and allow to come to room temperature before using.
To make muffins.
Preheat your oven to 350°F (for lighter, more delicate muffins) or 375°F (for darker, firmer muffins). Grease or line 9 cups of a standard 12-cup muffin tin, and set the tin aside.
Place the dry mix (495 grams for 9 muffins) in a large bowl. Loosen the mixture with a whisk and break up any large clumps.
Place the milk and eggs in a 2 cup measuring cup or small bowl. Whisk until very well-combined.
Pour the milk and egg mixture into the large bowl of dry ingredients, and mix until just combined. The mixture should be thick but soft.
Add the (optional) corn and mix just until the corn is evenly distributed throughout. Allow the batter to sit for 5 minutes.
Using a large spring-loaded ice cream scoop, fill the 9 prepared wells of the muffin tin full of batter, leaving the rounded tops from the scoop, if possible. Sprinkle each muffin top lightly with a few of the optional coarse sugar crystals.
Bake the muffins.
Place the tin in the center of the preheated oven, and pour the empty wells of the tin about 2/3 of the way full with tap water. Allow the muffins to bake until a toothpick inserted in the center of a muffin comes out with a few moist crumbs attached (about 20 minutes in a 350°F oven; about 18 minutes in a 375°F oven).
Remove from the oven and allow to cool in the pan for 10 minutes before transferring to a wire rack to cool completely.
Video
Notes
For the traditional 8 1/2-ounce size Jiffy-style corn muffin mix, simply halve all of the dry mix ingredients, and then the wet ingredients.Originally published on the blog in 2015. Video, many images, most text new; recipe mostly unchanged.