Preheat your oven to 350°F (175°C).
In a medium bowl, combine the graham cracker crumbs and melted butter until well mixed. Press the mixture firmly into the bottom of a 9x13-inch baking dish to form a crust.
Bake the crust in the preheated oven for 10 minutes, then remove it and let it cool slightly.
Pour the sweetened condensed milk evenly over the crust.
Sprinkle the chocolate chips and toffee bits over the condensed milk layer.
Bake for an additional 15 minutes, or until the chocolate chips are melted and bubbly.
Remove from the oven and let it cool completely. Once cooled, spread the whipped topping over the top.
If desired, sprinkle chopped pecans on top and drizzle with chocolate syrup.
Refrigerate for at least 2 hours before cutting into bars for easier serving.