1. Preheat oven to 350°F (175°C) and line an 8×8-inch pan with parchment paper.

2. Whisk melted butter with granulated sugar and brown sugar until glossy.

3. Beat in eggs and vanilla extract, then fold in sourdough starter.

4. Sift cocoa powder, flour, baking powder, and salt into the wet mixture and stir until just combined.

5. Fold in crushed freeze dried raspberries.

6. Pour batter into prepared pan and bake for 25–30 minutes until a toothpick comes out with moist crumbs.

7. Cool brownies completely in the pan, then remove and chill slightly for clean cuts.

8. Use a heart shaped cutter to cut brownies into 12 hearts.

9. Beat softened butter for frosting until fluffy.

10. Gradually add powdered sugar, then ground freeze dried raspberries and vanilla, mixing until combined.

11. Add cream one tablespoon at a time until the buttercream reaches a spreadable consistency.

12. Pipe or spread buttercream onto each brownie heart using an offset spatula.

13. Garnish with extra freeze dried raspberries if desired.