Preheat the oven to 350°F. Line an 8"x8" metal baking pan with parchment paper. Set the pan aside.
In a large, microwave-safe bowl, melt butter and chocolate in the microwave in 30 second increments. Whisk until smooth.
½ cup unsalted butter, 1 ½ ounces semi-sweet chocolate baking bar
Add both sugars and whisk until combined.
1 cup granulated sugar, ⅓ cup light brown sugar
Add eggs and vanilla and whisk until combined.
1 ½ teaspoons vanilla extract, 2 large eggs
Add flour, cocoa powder, and salt and fold into the sugar mixture until just a few streaks remain.
⅔ cup all-purpose flour, ⅔ cup Dutch-processed cocoa powder, ¾ teaspoon salt
Add chocolate chips and about ⅔ of the raspberries and fold into the batter. Reserve a few raspberries to add on top.
½ cup semi-sweet chocolate chips, 1 cup fresh raspberries
Spread the batter into the prepared pan.
Add raspberry preserves on top of batter in small dollops. Use a knife or offset spatula to swirl the preserves through the batter. Add the remaining raspberries on top.
2 Tablespoons raspberry preserves
Bake the brownies for 40-45 minutes. A toothpick inserted into the center should come out with a few moist crumbs but no raw batter. Let the brownies cool completely in the pan before removing them by lifting up on the edges of the parchment paper. Slice into 16 squares to serve.
Notes
Storage: Store leftover brownies in an airtight container in the fridge for up to 4 days.