Make the crust. Preheat the oven to 350°F. Beat the butter until creamy and smooth, then add flour, brown sugar, and salt. Mix until everything comes together in a soft, crumbly dough. Press most of this mixture into a greased 9x13 pan to form a solid crust, saving the rest for the topping. Bake 10–12 minutes, just until the edges turn lightly golden.
Prepare the chocolate layer. Melt part of the chocolate chips with the sweetened condensed milk in a small saucepan over medium heat. Stir continuously until the mixture becomes silky and completely smooth, then pour it evenly over the warm crust.
Add the topping. Stir the nuts into the remaining crumb mixture. Sprinkle this over the chocolate layer, letting some of the crumbs stay chunky for texture. Drop spoonfuls of raspberry jam over the top, letting it spread slightly. Finish by sprinkling the remaining chocolate chips across the surface.
Bake and cool. Bake 25–30 minutes or until the center looks set and the topping is lightly browned. Let cool completely — this helps the bars firm up and gives you cleaner slices.