Preheat oven to 350°F. Prepare three 8-inch cake pans with non-stick spray and parchment paper.

Mix dry ingredients: flour, cocoa, baking soda, and salt in a bowl.

Cream butter, sugar, oil, and vanilla in a large bowl until light and fluffy, about 3-4 minutes.

Add eggs one at a time, mixing well after each addition.

Alternate adding dry ingredients and milk to the batter, starting and ending with dry ingredients. Mix until just combined.

Divide batter evenly into prepared pans and bake for 22-25 minutes, or until a toothpick comes out with moist crumbs.

Cool cakes for 2-3 minutes in pans, then transfer to a wire rack to cool completely.

Prepare frosting by beating butter until smooth, then mix in melted chocolate and cocoa powder.

Gradually add powdered sugar, salt, and chocolate liqueur until desired consistency is reached.

Level cakes, brush with reserved chocolate liqueur, spread filling and frost layers, then assemble.

Make ganache by heating cream and pouring over chocolate chips, then whisk until smooth.

Pour ganache over the assembled cake, let set, and decorate as desired.