Preheat oven to 350°F. Line a 9" square baking pan with foil to overhang sides by 2". Coat with cooking spray. In microwave-safe bowl, microwave butter and unsweetened chocolate on high in 30 second intervals until melted and smooth. Cool to room temp.
Stir in sugar, 1/2 cup strawberry preserves, and strawberry extract, eggs, vanilla until combined. Add flour, cocoa and salt. Stir until blended. Stir in chocolate chips. Spread batter in pan.
Bake 40 min, or until toothpick inserted in center comes out clean. Cool in pan on rack.
Using foil, lift from pan. In bowl toss strawberries with 1/3 cup low-sugar preserves. Slice cooled brownie slices in half. Sandwich with whipped topping and strawberry mix. Top with additional topping and strawberries.