• Preheat the oven to 170°C. Prepare three small baking pans (diameter of 18 cm) with baking paper. If you have only 2 or 1 rotate them in the oven until there is no batter left.
• In a bowl whip the butter, oil and sugars until creamy. Now listen - make sure you cream these ingredients for at least 8 minutes or more. The mixture should get very creamy and light in colour.
• Add eggs, and mix again. Make sure you take time and let the mixture get twice its size. Scrape the bowl in the middle of the process.
• In another bowl mix flour, and baking powder. Pour milk into the glass with lemon juice. Add ⅓ of the flour mix and whisk on slow speed. Pour ½ of the milk and whisk on slow speed as well. Continue in the process until you add the flour mix last.
• Crush half of the Oreo into smaller and bigger pieces. Add them to the batter and fold them in with a rubber spatula.
• Divide the batter evenly between the baking pans. Bake for 35-45 minutes or until the toothpick comes out clean. Take the cakes out of the oven and let cool completely.

Cream

• Whip the whipping cream until stiff. Do not over-mix!
• In another bowl cream the mascarpone, and vanilla extract with butter. When the consistency is creamy, add icing sugar and whip at a very slow speed.
• Cut cool cakes into halves. Be careful - it can look they're a little bit dry and can fall apart easily. They get moist once the cream is added and they're rested in the fridge. Be careful while working with them. If one of the cake layers falls apart, don't worry. You can still stick them together with a frosting cream.
• Cut the top of the cake layer and add cream on top. Sprinkle with crushed Oreo cookies for frosting. Put another cake layer on top, add cream, and sprinkle with crushed Oreo cookies. Repeat the process.
• Cover the cake with the rest of the cream. Put into the fridge for 2 hours before decorating them with chocolate ganache.

Chocolate Ganache

• Pour melted chocolate into the warm whipping cream. Stir well until thick. Let cool to room temperature and then pour over the cake.
• Keep the cake in the fridge for at least 6 hours (in total) or overnight. It tastes the best on the second day.