Step 1: Prepare Your Pan - Start by preheating your oven to 350°F (175°C). Line a 9x13 inch baking pan with parchment paper, leaving some overhang for easy removal later.
Step 2: Combine Dry Ingredients - In a large mixing bowl, whisk together the old-fashioned oatmeal, all-purpose flour, light brown sugar, baking soda, salt, and cinnamon (if using). This will be the base for your bars.
Step 3: Mix Wet Ingredients - In another bowl, combine the canola oil, eggs, and vanilla extract. Whisk until well combined and slightly frothy.
Step 4: Combine Wet and Dry Mixtures - Pour the wet ingredients into the dry ingredients and mix until just combined. The batter will be thick and hearty.
Step 5: Layer the Base - Spread half of the oatmeal mixture evenly into the prepared baking pan. Use a spatula to press it down firmly to create a solid base.
Step 6: Add the Dulce de Leche - Drizzle the warmed dulce de leche over the base layer, spreading it out so it covers the oats evenly.
Step 7: Add the Chocolate Chips & Coconut - Sprinkle the flaked coconut and ½ cup semi-sweet chocolate chips over the dulce de leche layer.
Step 8: Add the Remaining Oatmeal Mixture - Take the remaining oatmeal mixture and crumble it over the top of the coconut and chocolate layer. Press down gently to ensure it sticks.
Step 9: Drizzle with Sweetened Condensed Milk - Drizzle the sweetened condensed milk over the top of the crumbled layer, ensuring it spreads out evenly.
Step 10: Add Roasted Cashews - Sprinkle the roasted cashews over the top for extra crunch and flavor.
Step 11: Bake - Place the pan in the preheated oven and bake for 25-30 minutes, or until the top is golden brown and the edges are slightly crispy.
Step 12: Finish with Dark Chocolate - Once baked, remove the bars from the oven and immediately drizzle the melted dark chocolate over the top. Allow it to cool in the pan for about 10 minutes before transferring it to a wire rack to cool completely.
Step 13: Slice and Serve - Once cooled, use the parchment overhang to lift the bars out of the pan. Slice into squares or rectangles and enjoy your delicious creation!
