Preheat and Prepare: Start by preheating your oven to 180°C (350°F). Grease a baking dish with a little vegetable oil to prevent sticking.
Mix Dry Ingredients: In a large bowl, combine the rolled oats, plain flour, baking powder, ground cinnamon, and vanilla sugar. Mix these together until evenly distributed.
Combine Wet Ingredients: In another bowl, whisk together the vegetable oil, egg, and sugar (or erythritol) until the mixture is smooth and well-blended.
Prepare Apples: Toss the chopped apples with lemon juice to keep them from browning and add a slight tanginess to the bars.
Combine and Mix: Add the wet ingredients to the dry ingredients and mix gently until just combined. Fold in the chopped apples and nuts if using.
Bake the Bars: Pour the mixture into the prepared baking dish, spreading it out evenly. Bake in the preheated oven for 25-30 minutes, or until the bars are golden and firm to the touch.
Prepare the Chocolate Drizzle: While the bars are baking, prepare the chocolate drizzle. Heat the whipping cream in a small saucepan over medium heat until it just begins to simmer. Remove from heat and add the chopped chocolate, stirring until it’s completely melted and smooth.
Drizzle and Serve: Once the bars are done, let them cool slightly in the dish. Drizzle the melted chocolate over the bars. Allow the chocolate to set slightly before cutting into squares.
