Preheating the Oven: Begin by preheating your oven to a temperature of 350 degrees Fahrenheit (175 degrees Celsius). This will ensure the oven reaches the optimal temperature for baking by the time you are ready to insert the pan.
Preparation of the Crust: In a sizable mixing bowl, combine the all-purpose flour, brown sugar, and softened butter. Utilize an electric mixer to blend these ingredients at a medium setting for approximately two to three minutes, until the mixture achieves a fine crumb-like consistency. Following this, transfer the mixture into an ungreased baking pan measuring 13x9 inches. Press the mixture firmly and evenly across the bottom of the pan to form the crust.
Preparation of the Turtle Layer: Place a small saucepan over medium heat. Into the saucepan, add butter and brown sugar. Stir continuously and allow the mixture to cook until bubbles appear consistently across the surface, which will take a few minutes. Continue to stir for an additional 30 to 60 seconds to slightly thicken the caramel, then remove the saucepan from the heat.
Assembling the Layers: Distribute the pecan halves evenly across the crust. Carefully pour the hot caramel mixture over the pecans, ensuring it is spread evenly.
Baking Process: Insert the pan into the preheated oven and bake for 18 to 20 minutes, until the entire surface of the mixture bubbles and the edges turn golden brown, indicating that it is thoroughly cooked.
Adding the Chocolate Topping: Upon removing the pan from the oven, place it on a wire cooling rack. Immediately sprinkle the milk chocolate chips over the hot surface of the bars. Allow the chocolate to melt for approximately two to three minutes. After melting, gently swirl the chocolate using a knife or small spatula to create a slightly marbled effect.
Cooling and Cutting the Bars: Allow the bars to cool completely at room temperature, which will take about 30 minutes. Once cooled, use a sharp knife to cut the bars into 48 equal portions. Clean the knife between cuts to ensure clean, sharp edges for each bar.