Preheat oven to 350°F. Lightly grease 9x13 baking dish or spray with nonstick cooking spray and line with parchment paper. Set aside.
In a large mixing bowl or the bowl of a stand mixer, cream butter and brown sugar together for 2 to 3 minutes, until light and creamy,
16 tablespoons unsalted butter, ½ cup light brown sugar
Mix in flour and salt until combined. Dough should be nice and crumbly.
2 cups all-purpose flour, ½ teaspoon salt
Set about ⅔ cup of the mixture aside for the crumb topping. Evenly press the remainder of the mixture into the bottom of the prepared baking dish. The layer will be relatively thin.
Bake for 10 minutes or until the crust just begins to have touches of golden brown.
Stir pecans into reserved crust mixture. Set aside. (This will be the crumb topping.)
½ cup chopped pecans
Combine sweetened condensed milk and bittersweet chips in a microwave safe dish and heat on medium heat, in 30 second intervals in microwave, stirring in between, until chocolate is melted and mixture is smooth.
14 ounces sweetened condensed milk, 1 cup bittersweet chocolate chips
Pour the chocolate mixture over the hot crust and use an offset spatula to spread evenly.
Sprinkle the crumb topping over the chocolate layer. Drop teaspoonfuls of raspberry preserves on top of crumb mixture. (If preserves are too thick, stir in 1 tablespoon of water.) Sprinkle with semi-sweet chocolate chips.
½ to ⅔ cup raspberry preserves, 1 cup semi-sweet chocolate chips
Bake for 25 minutes or until set. Cool completely, cut into bars and enjoy!