In a medium bowl, whisk together the flour, baking powder, baking soda, and salt. Set aside.

In a large mixing bowl, beat the butter and sugar on medium speed until light and fluffy, about 3-4 minutes.

Mix in the oil until smooth. Add the eggs one at a time, mixing well after each addition. Stir in the vanilla extract.

With the mixer on low speed, add the flour mixture in three additions, alternating with the buttermilk (start and end with the flour). Mix until just combined. Avoid over-mixing.

Divide the batter evenly between the prepared pans. Bake for 32-36 minutes, or until a toothpick inserted into the center comes out clean.

Let the cakes cool in the pans for 10 minutes before transferring to a wire rack to cool completely.

In a large bowl, beat the butter on medium speed until smooth and creamy.

Sift together the confectioners’ sugar, cocoa powder, and salt. With the mixer on low speed, gradually add this mixture to the beaten butter, allowing them to incorporate slowly.

As the frosting thickens, gradually add the heavy cream and vanilla extract, mixing on low speed until smooth. Increase to medium-high speed and beat for 3-4 minutes until light and fluffy. If needed, add more cream, one tablespoon at a time, until the frosting reaches a spreadable consistency.

Place one cooled cake layer on a serving plate. Spread frosting on top, then place the second cake layer on top. Frost the top and sides of the cake. Garnish and decorate as desired.