01 - Preheat oven to 350°F. Grease three 8-inch round cake pans and line with parchment paper.
02 - Whisk together flour, baking powder, baking soda, and salt in a medium bowl. Set aside.
03 - Beat butter and sugar in a large bowl until light and fluffy, approximately 3-4 minutes.
04 - Add eggs one at a time, beating thoroughly after each addition. Mix in vanilla and almond extracts.
05 - Gradually add flour mixture in three portions, alternating with buttermilk. Begin and end with flour mixture, mixing until just incorporated.
06 - Add green food coloring and mix until batter reaches desired vibrant green shade.
07 - Divide batter evenly among prepared pans. Bake for 25-30 minutes until toothpick inserted in center comes out clean.
08 - Let cakes cool in pans for 10 minutes, then transfer to wire racks to cool completely before frosting.
09 - Beat butter until creamy. Gradually incorporate powdered sugar on low speed. Add milk, vanilla, and salt. Beat on high speed until fluffy and smooth.
10 - Place one cake layer on serving plate. Spread with frosting, add next layer, and repeat. Frost top and sides of assembled cake.
11 - Decorate with green sprinkles or edible shamrocks. Optionally tint portion of frosting with additional green coloring for decorative accents.