Step 1: Preheat the Oven - Begin by preheating your oven to 350°F (175°C) to ensure even baking.
Step 2: Prepare Your Baking Pan - Line a 9x13 inch baking pan with parchment paper or grease it with butter.
Step 3: Cream the Butter and Sugars - In a large mixing bowl, cream together the butter, dark brown sugar, and white sugar until light and fluffy.
Step 4: Add Eggs and Vanilla - Beat in the eggs one at a time and mix in the vanilla extract.
Step 5: Incorporate Biscoff Spread - Add in the Biscoff spread and mix until well combined.
Step 6: Combine Dry Ingredients - Whisk together the flour, baking powder, and salt in a separate bowl, then gradually mix into the wet ingredients.
Step 7: Fold in Rolo Candies - Gently fold in the halved Rolo candies into the batter.
Step 8: Bake - Spread the batter into the prepared pan and bake for 25-30 minutes or until edges are golden brown and a toothpick comes out clean.
Step 9: Cool and Cut - Allow the bars to cool for 10 minutes, then lift them out and cool completely on a wire rack before cutting into squares.