Preheat oven to 350°F and spray two 8-inch cake pans with cooking spray. Line the bottoms with parchment paper and spray again.
Whisk together flour, cornmeal, baking powder, and salt. Set aside. In a separate bowl, combine sugar, maple syrup, eggs, cornmeal, and vanilla. Mix on medium speed with an electric mixer until well blended. Add half of flour mixture and half of milk. Mix well. Repeat with remaining flour mixture and milk.
Divide batter evenly between cake pans. Bake 25-27 minutes, or until golden brown and set in the center. Let cakes cool in pans 10-15 minutes, then transfer to a wire rack to cool completely. Brush bourbon over tops of cake layers.
To make the frosting, heat bourbon in a small saucepan over medium heat. Bring to a simmer. Let bourbon cook until reduced by half and measures ¼ cup. Remove from heat and let cool completely.
Cream butter on medium-high speed with an electric mixer. Add shortening and mix until well blended. Add maple extract, ¼ cup reduced bourbon, and half of powdered sugar. Mix on low speed until mostly combined, then medium-high speed until completely combined. Repeat with second half of powdered sugar.
To assemble, spread frosting between cake layers and then all over cake. Decorate with a drizzle of maple syrup if desired.