01 - Preheat oven to 350°F. Grease and line two 9-inch round cake pans with parchment paper.
02 - In a medium bowl, whisk together flour, cocoa powder, baking soda, and salt. Set aside.
03 - In a large bowl, beat sugar and oil until combined. Add eggs one at a time, mixing well after each addition.
04 - Stir in buttermilk, vanilla extract, vinegar, and green food coloring. Whisk until the mixture achieves uniform green color.
05 - Add dry ingredients to wet ingredients in two batches, mixing just until incorporated. Avoid overmixing.
06 - Divide batter evenly between prepared cake pans.
07 - Bake for 28–32 minutes, or until a toothpick inserted in center comes out clean.
08 - Let cakes cool in pans for 10 minutes, then turn out onto wire racks to cool completely.
09 - Beat cream cheese and butter together until smooth and fluffy. Add powdered sugar, vanilla, and salt; beat until light and creamy.
10 - Place one cake layer on serving plate. Spread frosting over top. Add second layer and frost entire cake.
11 - Decorate with green sprinkles or crumbs from trimmed cake edges if desired.