Prepare a 6 cup terrine dish by lining it with plastic wrap.
Make the almond brittle by melting the 1/2 cup sugar in a small sauce pan on low heat. Swirl the pan every once in a while, but don't stir the sugar as it melts and turns brown. As soon as all the sugar is completely dissolved, remove from the heat and stir in the almonds. Immediately pour and spread the mixture onto a Silpat or similar non-stick surface. Allow to cool to room temperature, then use a rolling pin to break the brittle into small pieces.
As the almonds are cooling, melt the chocolate in a double boiler. When it has melted, stir in the butter, one tablespoon at a time, then remove from heat.
Meanwhile, separate the eggs into two large mixing bowls. Beat the egg whites until stiff and set aside. Beat the yolks with the 3 tablespoons of sugar until light colored and fluffy - about 2 minutes. Stir the melted chocolate and butter into the egg yolks and sugar. Stir just until blended. Gently fold in the egg whites just until combined.
Pour 1/2 of the chocolate mousse into the prepared terrine dish. Layer with the raspberries, then the candied almonds. Top with the remaining mousse. Cover with plastic wrap and place a weight on top, then refrigerate for 12 hours or overnight.
To serve, you can turn the terrine out onto a serving dish and slice, or just scoop from the terrine dish.
Makes 6 servings.