For the rice:
Combine the rice, water, butter, and kosher salt in a medium saucepan. Bring the water to a boil over medium heat, stir to blend.
Cover and reduce the heat to low for 20 minutes. Remove the pan from the heat, keep the pan covered for an additional 5 minutes. Gently fluff the rice with a fork.
For the waffles:
Place the egg whites in a small bowl and beat until the egg whites are stiff but not dry.
In a large bowl whisk together the flour, baking powder, baking soda, kosher salt, and sugar.
Add the egg yolks along with the melted shortening and the vanilla extract to the buttermilk. Whisk until fairly smooth.
Combine the buttermilk mixture with the dry ingredients, stirring until just combined. Batter will be somewhat lumpy.
Fold in the cooked rice and the beaten egg whites. Let the batter rest for 10 to 15 minutes.
Lightly season the surface of a waffle iron (with vegetable oil, butter, or a cooking spray) and set the heat on medium.
When the waffle iron is hot, ladle about ¼ cup batter into each section of the waffle iron. Cook the waffles for 3 to 5 minutes or until the waffle is crispy and golden brown.
If you’re making multiple batches, keep the cooked waffles warm by placing them on a baking rack in a 200-degree oven.