Prepare the Shortbread Crust:

1. Preheat the Oven: Preheat your oven to 350°F (175°C). This temperature is perfect for baking the crust to a light golden color.
2. Mix Ingredients: In a large mixing bowl, combine 2 cups of all-purpose flour, 1/2 cup of powdered sugar, and 1 cup of softened unsalted butter. Use a hand mixer or pastry cutter to blend the mixture until it forms a crumbly dough.
3. Press the Dough: Grease a 9×13-inch baking pan and press the dough evenly into the bottom. Use your hands or a spatula to create a smooth layer.
4. Bake: Bake for 15-20 minutes, or until the edges are lightly golden. Set aside to cool while you prepare the caramel.

Make the Caramel Layer:

1. Melt the Butter: In a medium saucepan, melt 1 cup of unsalted butter over medium heat.
2. Add Sugar and Corn Syrup: Stir in 1 cup of packed brown sugar and 1/4 cup of light corn syrup. Continue stirring until the mixture starts to bubble.
3. Add Condensed Milk: Reduce the heat to low and add 1 can of sweetened condensed milk. Stir constantly to prevent sticking.
4. Simmer: Let the mixture simmer for 5-7 minutes until it thickens and turns a deep caramel color.
5. Spread the Caramel: Pour the caramel evenly over the cooled shortbread crust, spreading it with a spatula for an even layer.

Add the Pecan Layer:

1. Chop Pecans: Coarsely chop 2 cups of pecans. The mixture of small and large pieces adds great texture to the bars.
2. Toast the Pecans: Sprinkle the chopped pecans over the caramel layer. Return the pan to the oven and bake for an additional 10-15 minutes, until the caramel is bubbly and the pecans are lightly toasted.

Create the Chocolate Topping:

1. Add the Chocolate: Remove the bars from the oven and immediately sprinkle 1 1/2 cups of semisweet chocolate chips over the hot caramel and pecans.
2. Melt and Spread: Allow the chocolate to sit for a few minutes to melt, then use a spatula to spread it evenly, creating a smooth, glossy layer.

Cool and Set:

1. Cool at Room Temperature: Let the bars cool completely at room temperature. This allows the layers to firm up before refrigerating.
2. Refrigerate: Once cooled, refrigerate the bars for at least 1 hour to set the chocolate completely, making it easier to cut the bars.

Cut and Serve:

1. Cut the Bars: Once the bars have set, use a sharp knife to cut them into squares. For cleaner cuts, dip your knife in hot water and wipe it dry between cuts.
2. Store: Store the bars in an airtight container at room temperature for up to a week, or refrigerate for longer freshness.