Preheat oven to 350°.
To prepare cake, coat 2 (9-inch) round cake pans with cooking spray; line bottom of pans with wax paper. Coat wax paper with cooking spray; set aside.
Combine the hot water and 2 tablespoons espresso in a small bowl, stirring to dissolve; set aside. Lightly spoon flour into dry measuring cups; level with a knife. Sift together flour, baking soda, and salt; set aside.
Combine the granulated sugar and 1/4 cup brown sugar. Place 1/4 cup sugar mixture, shortening, and vanilla in a large bowl; beat with a mixer at low speed 30 seconds or until well combined. Increase speed to medium; add remaining sugar mixture, 1/4 cup at a time, beating 15 seconds between each addition. Scrape sides of bowl; beat an additional 5 minutes. Add eggs, 1 at a time, beating 1 minute after each addition. Add espresso mixture, beating until well combined. Add flour mixture and buttermilk alternately to egg mixture, beginning and ending with flour mixture. Pour batter into prepared pans. Bake at 350° for 30 minutes or until a wooden pick inserted in center comes out clean. Cool in pans 10 minutes on a wire rack; remove from pans. Cool completely on wire rack. Discard wax paper.
To prepare frosting, melt butter in a medium, heavy saucepan over medium heat. Add 1/2 cup brown sugar; cook 3 minutes or until mixture is smooth, stirring frequently with a whisk. Stir in the evaporated milk, 1 tablespoon at a time; cook 3 minutes or until mixture resembles caramel sauce. Remove from heat; stir in 2 teaspoons espresso. Cool to room temperature. Stir in vanilla. Gradually add powdered sugar, stirring with a whisk until smooth.
Place 1 cake layer on a plate; spread with 1/2 cup frosting. Top with remaining cake layer; spread remaining frosting over top and sides of cake. Arrange coffee beans around top edge of cake, if desired. Let cake stand 1 hour or until frosting is set.