1. 1. Prepare Your Pan: Line an 8×8 inch baking pan with parchment paper, leaving an overhang on the sides. This will make it much easier to lift the bars out once they’re set.

2. 2. Melt Wet Ingredients: In a medium saucepan, combine the 1/2 cup butter, granulated sugar, brown sugar, and milk. Cook over medium heat, stirring constantly, until the butter is melted and the sugars are dissolved. Bring the mixture to a gentle boil and let it boil for exactly one minute, continuing to stir. This helps create the right consistency.

3. 3. Add Flavor and Oats: Remove the saucepan from the heat. Stir in the vanilla extract, then add the quick-cooking oats and 1/2 cup creamy peanut butter. Mix well until everything is thoroughly combined and the oats are evenly coated. The mixture will be thick and sticky.

4. 4. Press into Pan: Transfer the oat mixture to your prepared 8×8 inch pan. Using the back of a spoon or your hands (lightly greased if it’s too sticky), press the mixture down firmly and evenly into the pan. Make sure it’s packed tightly to form a solid base for the bars.

5. 5. Prepare Chocolate Topping: In a microwave-safe bowl, combine the 1 cup semi-sweet chocolate chips and 1 tablespoon butter. Microwave in 30-second intervals, stirring after each, until the chocolate is melted and smooth. Alternatively, you can melt them in a double boiler on the stovetop.

6. 6. Top and Chill: Pour the melted chocolate mixture evenly over the oat base in the pan. Spread it gently with a spatula to cover the entire surface.

7. 7. Set the Bars: Place the pan in the refrigerator for at least 30-60 minutes, or until the chocolate topping is completely set and firm. This is important for clean slices.

8. 8. Slice and Serve: Once firm, use the parchment paper overhang to lift the entire block of bars out of the pan. Place it on a cutting board and slice into squares or rectangles. Enjoy your delicious no-bake oatmeal cookie bars!