Start by heating your oven to 350°F (175°C). Lightly grease two 8-inch cake pans, then line the bottoms with parchment paper to prevent the cakes from sticking.

Add the flour, baking powder, and salt to a medium bowl. Whisk everything together until evenly blended, then set the bowl aside while you prepare the batter.

Place the softened butter and sugar in a large mixing bowl. Beat them together for several minutes until the mixture becomes pale, fluffy, and noticeably lighter in texture.

Crack in the eggs one at a time, mixing well after each addition. Pour in the vanilla extract, bourbon, and vegetable oil, then continue mixing until the batter looks smooth and well combined.

Add about one-third of the flour mixture to the bowl and mix gently. Pour in half of the milk and stir again. Repeat with another portion of flour, the remaining milk, and finally the rest of the flour. Mix just until no dry streaks remain.

Divide the batter evenly between the prepared pans and smooth the tops. Place them in the oven and bake for 30 to 35 minutes, or until a toothpick inserted into the center comes out clean.

Remove the pans from the oven and allow the cakes to rest for 10 minutes. Carefully turn them out onto a wire rack and leave them to cool completely before adding the frosting.

Add the softened butter to a large mixing bowl and beat until smooth and creamy. Gradually mix in the confectioners’ sugar, then add the bourbon, milk, and vanilla extract. Continue beating until the frosting becomes light, fluffy, and easy to spread.

Spread a layer of buttercream over the first cake layer, then place the second layer on top. Cover the top and sides of the cake with the remaining frosting, smoothing it evenly with a spatula. Slice into portions and serve.