Preheat the oven to 180°C (350°F). Butter and line the bottom of two 20-cm (8-inch) square baking dishes with parchment paper, leaving some overhang on two sides. Place them on a baking sheet.
For the caramel sauce, in a saucepan, bring the sugar, Scotch, water, and corn syrup to a boil. Cook without stirring until the mixture turns golden. Remove from heat and gradually add the hot cream and butter. Bring to a boil again, stirring until smooth. Divide the caramel between the baking dishes and sprinkle with half of the pecans.
For the cake, in a bowl, combine the flour, chopped pecans, baking soda, and salt. Set aside.
In another bowl, cream together the butter, oil, brown sugar, and vanilla using an electric mixer. Add the eggs one at a time, beating until smooth. At low speed, add the dry ingredients alternately with the buttermilk.
Carefully divide the batter between the baking dishes over the caramel. Bake for about 50 minutes. Let cool for 30 minutes.
Invert one cake onto a serving platter. Invert the second cake onto a baking sheet and slide it onto the first cake. Allow to cool completely.
Serve warm or cold, topped with whipped cream if desired. Enjoy!