Preheat oven to 325ºF. Line an 8 x 8-inch baking pan with parchment paper, leaving a couple of inches of overhang.
In a medium bowl, sift together flour, cocoa powder and salt.
In a large heat safe bowl, melt butter together with chocolate, in the microwave or on the stovetop over a pan or barely simmering water. Stir until smooth.
Beat sugar into butter and chocolate mixture until well combined.
Add eggs, egg yolk and vanilla to chocolate mixture and whisk until smooth.
Fold in flour mixture until combined, scraping the bottom of the bowl as needed.
Transfer batter to 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 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 reduced purée in saucepan. Heat until bubbles start to form around the edges. Do not boil.
Pour over white chocolate and let stand 5 minutes. Stir until smooth and well combined. Spread over cooled brownies.