Preheat oven to 375°F. Line two baking sheets with parchment paper and set aside.
Beat shortening and brown sugar in a large bowl until creamy, about 1-2 minutes. Add the egg and vanilla extract, then mix again, stopping to scrape the bottom and sides of the bowl.
1 1/3 cup shortening*, 2 cups light brown sugar, 2 large eggs, 2 teaspoons vanilla extract
Add flour, baking soda, baking powder, and salt. Mix just until combined.
2 cups all-purpose flour, 1/2 teaspoon baking soda, 1/4 teaspoon baking powder, 1/2 teaspoon salt
Stir in the cornflakes, oats, and walnuts.
1 1/2 cups old-fashioned oats, 2 cups cornflakes, 1 cup walnuts
Use a medium cookie scoop to drop balls of dough onto the prepared baking sheet, spacing them a couple inches apart so they have room to spread. Bake for 9-11 minutes until just golden brown around the edges and on top.