Combine flour and cocoa powder in medium bowl. Cut in butter using pastry blender or 2 forks until mixture resembles coarse crumbs. Stir in whipping cream just until mixture comes together. Divide dough in thirds. Wrap each in plastic food wrap and refrigerate 1 hour or up to overnight.
Heat oven to 375°F.
Roll out dough on lightly floured surface (keeping remaining dough refrigerated) to ¼-inch thickness. Cut with 1 ½-inch heart-shaped cookie cutter. Coat both sides with sugar. Place on parchment-lined baking sheet. Prick several times with fork.
Baked 6-8 minutes. Remove from cookie sheet immediately; place on cooling rack
Combine powdered sugar, ¼ cup butter, mashed raspberries and raspberry extract in bowl. Beat at medium speed, scraping bowl often, until light and fluffy.
Place 1 teaspoon filling onto 1 cookie, bottom-side up. Top with second cookie, bottom-side down.
