Preheat the oven to 350°F (175°C) and grease a 9×13-inch baking pan.

In a medium bowl, combine 1 ½ cups of flour, ½ cup of brown sugar, and ½ teaspoon of cinnamon with 2/3 cup of softened unsalted butter. Mix until crumbly and press into the prepared pan evenly.

Bake the crust for about 10–12 minutes, or until it turns lightly golden brown. Remove from oven and let cool slightly.

Beat cream cheese until smooth in a separate bowl. Add 2 tablespoons of flour, ½ cup of granulated sugar, and 2 large eggs. Mix until smooth and creamy.

Fold in 6 ounces of semisweet chocolate chips gently into the cream cheese mixture.

Pour the cream cheese and chocolate mixture over the pre-baked crust and spread it evenly.

Bake for 20–25 minutes until the topping is set, firm but slightly soft in the center. Allow to cool in the pan.

Melt the remaining 6 ounces of semisweet chocolate chips and spread generously over the cooled bars.

Sprinkle the chopped toasted pecans or walnuts on top of the melted chocolate.

Cool completely before cutting into squares.