Preheat the oven to 350 degrees

Butter and flour three 7-inch cake pans. Line with parchment paper circles.

Cut the butter into cubes, and coarsely chop the chocolate. Melt the butter and chocolate together at low heat in a large saucepan. Let cool.

Beat the light brown sugar, granulated sugar and eggs until light and airy, about 3 minutes.

Mix the flour, cocoa powder and baking powder in a separate bowl.

Pour the chocolate and butter mixture into the sugar and egg mixture, and beat to a smooth batter. Sift in the dry ingredients, and mix until the batter is smooth. Divide the batter evenly among the cake pans, and level the surface with an offset spatula. Press a portion of the raspberries into each cake layer; set aside the remainder for decoration.

Bake the layers for 40-45 minutes or until a toothpick inserted into the center comes out with moist crumbs.

Pour the egg whites and sugar into a heatproof bowl. Place it on top of a double boiler over a pot of simmering water. Whisk continually until the mixture reaches 150 degrees Farenheit or the sugar crystals have dissolved. Remove the bowl from heat.

Continue to beat the mixture with an electric beater or hand mixer until it is as white and fluffy as a meringue. Beat until the mixture is cool, up to 10 minutes.

Add the butter a little at a time. After all the butter has been incorporated, beat for another 3-5 minutes.

Purée the raspberries in a blender. Press the purée through a fine mesh to remove the seeds.

Mix the purée with the buttercream, beating until smooth. Add a tiny amount of gel colour to make it more pink.

Break the chocolate into pieces and dice the butter.

Carefully melt the butter with the chocolate in a saucepan over low heat, and let it cool. The glaze will thicken somewhat but still be fluid.