Preheat oven to 325ºF (165ºC). Line an 8-inch square baking pan with parchment paper, leaving a couple of inches of overhang.
In a medium bowl, sift together the flour, cocoa powder and salt.
In a large heat safe bowl set over a pot of barely simmering water, melt the butter and chocolate together, stirring occasionally, until smooth.
Beat the sugar into butter and chocolate mixture until well combined.
Add the eggs, egg yolk and vanilla to the chocolate mixture and whisk until smooth.
Fold in the flour mixture until combined.
Transfer the batter to the prepared baking pan. Bake until a toothpick inserted in the center comes out with moist crumbs on it, about 25-30 minutes. Do not over bake. Let cool completely.
Place the white chocolate in a medium bowl.
In a small saucepan over medium-low heat, simmer raspberry purée until reduced by half. Combine heavy cream with the reduced purée in saucepan. Heat until bubbles start to form around the edges. Do not boil.
Pour the hot cream mixture over the white chocolate, making sure its completely submerged, and let stand 5 minutes. Stir until smooth and well combined. Spread over the cooled brownies.