To make the Truffle Filling:

• Add the chocolate chips to a medium sized bowl.
• Combine the chocolate liqueur and heavy cream in a microwave safe measuring cup and microwave just until it begins to boil.
• Pour the hot cream mixture over the chocolate chips and allow to sit for 2-3 minutes, then whisk until smooth. Cover and put the chocolate mixture in the fridge until cooled.

To make the Cake Layers:

• Preheat oven to 350°F (176°C) and prepare three 8 inch cake pans with non-stick baking spray and parchment paper in the bottom.
• Combine the flour, cocoa, baking soda and salt in a medium sized bowl and set aside.
• Add the butter, sugar, oil and vanilla extract to and large mixer bowl and beat together until light in color and fluffy, about 3-4 minutes. Do not skimp on the creaming time.
• Add the eggs one at a time, mixing until mostly combined after each. Scrape down the sides of the bowl as needed to be sure all ingredients are well incorporated.
• Add half of the dry ingredients to the batter and mix until mostly combined.
• Slowly add the milk and mix until well combined. The batter will look curdled, but that’s ok.
• Add the remaining dry ingredients and mix until well combined and smooth. Scrape down the sides of the bowl as needed to be sure all ingredients are well incorporated. Do not over mix the batter.
• Divide the batter evenly between the prepared cake pans and bake for 22-25 minutes, or until a toothpick comes out with a few moist crumbs.
• Remove cakes from the oven and allow to cool for 2-3 minutes, then remove to a cooling rack to finish cooling. Reserve the chocolate liqueur for the cake layers for later.

To make the Chocolate Frosting:

• Add the butter to a large mixer bowl and beat until smooth.
• Add the melted chocolate and mix until well combined.
• Add the cocoa powder and mix until well combined.
• Add about half of the powdered sugar, salt and half of the liqueur and mix until well combined.
• Add the remaining powdered sugar and mix until smooth.
• Add the remaining liqueur as needed to get the right consistency of frosting. Set frosting aside.

To build and finish the Cake:

•  To layer the cake, first use a large serrated knife to remove the domes from the tops of the cakes so they are flat. See my tips on how to level a cake and how to stack a cake.
• Place the first cake layer on a serving plate or on a cardboard cake circle.
• Add the chocolate liqueur for the chocolate cake that was reserved before to a small bowl and use a pastry brush to brush the cake with about 1/2 of the liqueur.
• Pipe a dam around the edge of the cake layer with some of the chocolate frosting.
• Spread about 1/2 of the chocolate truffle filling on top of the cake, in the center of the dam.
• Add the second layer of cake, then repeat steps 20 thru 22.
• Add the third and final layer of cake on top.
• Frost the top and outside of the cake with the remaining chocolate frosting. You can refer to my tutorial for frosting a smooth cake, if you’d like.
• To make the ganache topping, add the chocolate chips to a medium sized bowl (see my tips on making chocolate ganache).
• Combine the heavy whipping cream and chocolate liqueur in a microwave-safe measuring cup and microwave until it just begins to boil.
• Pour the hot cream mixture over the chocolate chips and let it sit for 2-3 minutes, then whisk until smooth.
• Drizzle the chocolate ganache around the edges of the cake, then fill in the center. See my tips on making a chocolate drip cake.
• Use the remaining frosting to pipe swirls around the edge of the cake, then top the swirls with Lindor truffles.
• Refrigerate the Chocolate Truffle cake if it’ll sit for more than 24 hours. Cake is best served at room temperature and should last best for about 3 days. Serve slices of cake with little drizzle of the chocolate liqueur on the plate, if desired.