Preheat oven to 350°F (175°C). Grease and line two 8-inch (20 cm) round cake pans.
Whisk together flour, cocoa powder, baking powder, baking soda, and salt in a bowl.
In another bowl, beat sugar, eggs, and oil until light and fluffy. Add buttermilk, coffee, Baileys, and vanilla; mix until combined.
Gradually fold the dry ingredients into the wet mixture until smooth.
Divide batter evenly between pans and bake for 30–35 minutes, or until a toothpick inserted in the center comes out clean.
Cool completely before frosting.
2. Make the Baileys Buttercream:
Beat butter for 2–3 minutes until creamy.
Gradually add powdered sugar, cocoa powder, and salt on low speed.
Mix in Baileys and vanilla; beat until light, fluffy, and silky smooth.
3. Assemble the Cake:
Place one cake layer on a serving plate and spread a generous layer of frosting on top.
Add the second cake layer and cover with remaining frosting.
Optional: drizzle with melted chocolate or dust with cocoa powder for an elegant finish.
